OPINION
DALLY, Judge.This is a post-conviction writ of habeas corpus proceeding.
On May 15,1975, petitioner was convicted for a violation of the Controlled Substances Act, the alleged offense being possession of phentermine. The punishment assessed was imprisonment for five years. On appeal, the contention now presented was not raised and the judgment was affirmed in a per curiam opinion.
Petitioner now contends, and the State in its brief agrees, that he is unlawfully imprisoned for the reason stated in Riddle v. State, 560 S.W.2d 642 (Tex.Cr.App.1977) and Lumberas v. State, 560 S.W.2d 644 (Tex.Cr.App.1977). In those cases, involving prosecutions for a misdemeanor under the Dangerous Drugs Act, Art. 4476-14, V.A.C.S., we stated that phentermine had been removed from the Dangerous Drugs Act and placed in Schedule IV of the Controlled Substances Act, Art. 4476-15, V.A. C.S., but phentermine had not been added to any of the penalty groups of the Controlled Substances Act. We said that as a consequence no penalty was provided for the possession or delivery of phentermine.
We have reexamined the opinions in Riddle and Lumberas in light of the opinion in Ex parte Ashcraft, 565 S.W.2d 926 (Tex.Cr.App.1978). This reexamination convinces us that we were correct in holding that phentermine was not a dangerous drug and in reversing those convictions under the Dangerous Drugs Act. At the time Riddle and Lumberas were decided, Sec. 2(a) of the Dangerous Drugs Act provided, among other things, that a dangerous drug was “any drug or device that is not included in Schedules I through V of the Texas Controlled Substances Act . . . ” Phentermine was, and is, listed in Schedule IV of the Controlled Substances Act, Sec. 2.06(d)(2). Also, isomers of methamphetamine were, and are, listed in Schedule II of the Act, Sec. 2.04(d)(2).1 However, we erred when *907we went on to state, in dictum not necessary to the result reached in Riddle and Lumberas, that phentermine was not included in a penalty group of the Controlled Substances Act and there was no penalty provided for its possession or delivery.
Methamphetamine, including its salts, isomers, and salts of isomers, has always been listed in Penalty Group One of the Controlled Substances Act, Sec. 4.02(b)(6). Isomeric compounds are composed of the same elements united in the same proportions by weight, but differ in one or more properties because of a difference in structure. Webster’s New International Dictionary (2d ed. 1957). Methamphetamine and phentermine have the same chemical composition, noted as CioHjbN, and have the same molecular weight, 149.2. Merck Index, pp. 775, 944 (9th ed. 1976); Martindale, The Extra Pharmacopoeia, pp. 86, 314 (27th ed. 1977). Methamphetamine and phenter-mine are structural isomers, i. e., compounds having the same chemical composition, but differing in the arrangement of the component elements. 15 Encyclopedia Americana, p. 514 (1976). The testimony of Floyd E. McDonald, Director of the Houston Police Laboratory, which appears in the records of this Court from the previous appeal of this case, is consistent with this conclusion. He testified phentermine is an isomer of methamphetamine.
Since phentermine is an isomer of methamphetamine, we were in error when we stated in Riddle and Lumberas that there was no penalty provided for its possession or delivery. Phentermine was then and is now a controlled substance, and was then and is now subject to criminal prosecution under the Controlled Substances Act. On the other hand, we were correct in denying relief in Ashcraft, since in that case the State was prosecuting the felony offense and had alleged that phentermine is an isomer of methamphetamine.
The indictment on which petitioner was convicted alleges that on or about July 26, 1974, petitioner “knowingly and intentionally possessed] a controlled substance, namely: phentermine . . .” Unlike the indictment in Ashcraft, the indictment does not allege that phentermine is an isomer of methamphetamine. Thus, we are called upon to determine whether such an allegation is necessary in order to prevent the indictment from being fundamentally defective.
In Taylor v. State, 172 Tex.Cr.R. 461, 358 S.W.2d 124 (Tex.Cr.App.1962), a prosecution under the old Narcotic Drug Act, Art. 725b, V.A.P.C. (1925), the indictment alleged the unlawful possession of “a narcotic drug, to-wit: dolophine . . . ” Dolophine was not specifically named in Art. 725b, supra, but the proof showed that it was a narcotic drug of the same chemical formula as ami-done, which was named in the Act. We held that the indictment was sufficient to allege an offense and not fundamentally defective.
In Henley v. State, 387 S.W.2d 877 (Tex.Cr.App.1964), the indictment alleged the unlawful sale of “a narcotic drug, to-wit: Paregoric . . . ” We held that the trial court did not err in overruling the defendant’s motion to quash the indictment, stating:
“While paregoric is not included within the statutory definition of a narcotic drug, the proof shows that it is, in fact, a narcotic drug known under the official name of ‘camphorated tincture of opium’ and that it contains morphine which comes from opium, a narcotic drug enumerated in the statute.”
*908In McClanahan v. State, 394 S.W.2d 499 (Tex.Cr.App.1965), the defendant was charged with the unlawful sale of “a narcotic drug, to-wit: demerol . . . ” We held that while Demerol was not named in Art. 725b, supra, the trial court did not err in instructing the jury that Demerol was a narcotic drug, since the proof showed that Demerol was the trade name of isonipe-caine, which was named in the Act. On rehearing, we further held that the indictment was not unconstitutionally indefinite.
In Crockett v. State, 511 S.W.2d 519 (Tex.Cr.App.1974), the information alleged the unlawful attempt to obtain “a dangerous drug, to-wit: Talwin, by use of a forged prescription. . . .” We held that the information was fundamentally defective since Talwin was not named in the applicable statute, former Art. 726d, Sec. 2, V.A. P.C. (1925). We rejected the State’s argument that the information was sufficient to state an offense because the proof showed that Talwin was a legend drug, and hence a dangerous drug under Sec. 2(20) of Art. 726d, supra.
In Jackson v. State, 572 S.W.2d 551 (Tex.Cr.App.1978), the information alleged the unlawful possession of “a dangerous drug, namely TETRACYCLINE . . Noting that tetracycline is not specifically designated a dangerous drug under the Dangerous Drugs Act, Art. 4476-14, V.A. C.S., we held that the information was fundamentally defective based on the decision in Crockett.
Our opinions in Taylor, Henley, and McClanahan are in conflict with our more recent opinions in Crockett and Jackson. We are satisfied that the rule stated in the latter opinions is correct, and accordingly we overrule Taylor, Henley and McClana-han to the extent they conflict with Crockett, Jackson and this case.
Ex parte Charles, 582 S.W.2d 836 (Tex.Cr.App.1979), was a felony prosecution under the Dangerous Drugs Act for delivery of sinequan. Sinequan is not named in Sec. 2(a) of the Act, but is a legend drug and therefore subject to the Act. However, the indictment in Charles did not allege that sinequan is a legend drug, and we held that this omission rendered the indictment ineffective to state an offense. We stated the reason for this holding as follows:
“[Sjinequan is not listed by name in the Dangerous Drug Act; therefore, it is necessary to allege facts showing why sine-quan is a dangerous drug. An indictment should allege all that the State is required to prove. Art. 21.03, V.A.C.C.P., and see Benoit v. State, 561 S.W.2d 810 (Tex.Cr.App.1977).
“Drugs which bear a legend: ‘Caution: federal law prohibits dispensing without a prescription’ are dangerous drugs. Art. 4476-14, Sec. 2(a)(3), V.A.C.S. Assuming that sinequan is a dangerous drug because it bears that legend, it would be necessary for the State to prove that it was a dangerous drug because it bears that legend. Since an indictment should allege all that the State is required to prove, Art. 21.03, V.A.C.C.P., and Benoit v. State, supra, it would be essential for the State to allege that sine-quan is a dangerous drug because it bears the legend: ‘Caution: federal law prohibits dispensing without a prescription.’ The indictment fails to allege an essential element of the offense, because it fails to allege why sinequan is a dangerous drug. The relief sought must be granted.” 582 S.W.2d at 837.
The same reasoning is applicable to the instant case. Petitioner was indicted for possession of phentermine. Phentermine is not named in a penalty group of the Controlled Substances Act, but is subject to the Act because it is an isomer of methamphetamine. Since it was necessary for the State to prove that phentermine is an isomer of methamphetamine in order to convict petitioner, it was equally necessary for the State to allege this fact in the indictment.
To state the rule generally, we hold that in a prosecution under the Controlled Substances Act for the manufacture, delivery, or possession of a substance not specifically named in a penalty group but which is otherwise described in a penalty group (for example, an isomer of methamphetamine), *909such description is an essential element of the offense which must be alleged in the indictment in order to state an offense. The same rule applies to prosecutions under the Dangerous Drugs Act involving a drug not specifically named in Sec. 2(a) but which is otherwise described therein (for example, a legend drug).
The indictment in this case does not allege that phentermine is an isomer of methamphetamine; that is, the indictment does not allege why phentermine, a substance not listed by name in a penalty group, is a controlled substance. Therefore, the indictment fails to allege an essential element of the offense and is fundamentally defective. The relief sought is granted.
It is so ordered.
DOUGLAS, J., dissents.. Effective May 2, 1979, Sec. 2(a) of the Dangerous Drugs Act was amended to read:
“(a) The term ‘dangerous drug’ means any drug or device that is not included in Penalty *907Groups I through IV of the Texas Controlled Substances Act and that is unsafe for self-medication, and includes the following:
“(1) Procaine, its salts, derivates, or compounds or mixtures thereof except ointments and creams for topical application containing not more than two and one-half percent (2'⅛ %) strength.
“(2) Any drug or device which bears or is required to bear the legend: Caution: federal law prohibits dispensing without prescription, or the legend: Caution: federal law restricts this drug to use by or on the order of a licensed veterinarian.”
This amendment does not alter our conclusion that phentermine is not a dangerous drug. Isomers of methamphetamine, of which phen-termine is one, are listed in Penalty Group One of the Controlled Substances Act, Sec. 4.02(b)(6),