﻿Vol. 6 I.] GENERA AND SPECIES OF LYTOGERATID^. 145 



The following are the notices of Mr. Thompson's species, with 

 remarks on certain allied forms to which consideration has to be 

 given. 



Alocolytoceras Germaini (d'Orbigny). (Fig. 3, p. 152.) 



1845. Ammonites Germaini, d'Orbigny, ' Pal. Franc. Ten*. Jur. : Cephalopodes ' 

 p. 320 & pi. ci, figs. 4-5 only. 



Dr. Pompeckj x chooses the form above-quoted to be the type of 

 d'Orbigny's species, and therefore it is necessary to follow him. 

 But I cannot agree with him, that what he figures as the smooth 

 form of this species, really belongs to it (op. cit. fig. 27, p. 145). 

 It is a smooth form, which has the inner whorls of the Germaini- 

 stage certainly ; but, surely, it is of another stock altogether : the 

 long lobes and the broad inner margin of the stout whorls are 

 characters which, in my opinion, separate it from any of the three 

 genetic series now under consideration. 



Alocolytoceras Pompeckji, nom. nov. 



1845. Ammonites G-ermaini, d'Orbigny, ' Pal. Franc. Terr. Jur. : Cephalopodes ' 

 p. 320 & pi. ci, figs. 1-2 (not 4-5, and not 6). 



Description. — Dr. Pompeckj described this form as follows: — 



' Lytoceras, n. sp. Rarer than the preceding species [ Germaini), with higher 

 whorls, with more oval cross-section and more closely-set ribs.' (Op. cit. 

 p. 146.) 



Remarks. — Although Dr. Pompeckj separated this form, he did 

 not name it, and so I have much pleasure in dedicating it to him, as a 

 mark of appreciation of the value of his critical studies, particularly 

 in regard to his revision of Quenstedt's last work. 



Alocolytoceras diltjcidum (Oppel). 



In naming his species, Oppel gave as a synonym a term of 

 Quenstedt's, which that author had applied as the designation for 

 'A. cornucopia? d'Orbigny tab. 99.' Quenstedt did not quote any 

 figure of d'Orbigny's plate, and therefore I presumed that he meant 

 figs. 1 & 2 ; 2 but Dr. Pompeckj has now figured one of Oppel's 

 types, 3 from which it is evident that Oppel and Quenstedt intended 

 d'Orbigny's pi. xcix, fig. 4. 



The question now is, what must be taken as the holotype of 

 Oppel's species? It seems to me that, as Oppel gave a definite 

 reference which led to d'Orbigny's pi. xcix, one of the species 

 thereon must be the holotype. As it is now seen that fig. 4 was 

 intended, therefore that must be the holotype. Oppel's other 

 examples must be regarded as paratypes ; and it does not neces- 

 sarily follow that they belong to the same species as the holotype — 

 that is far too often the result in such cases. The original references, 

 therefore, would be : — Al. dilucidum (Oppel) : Description — ' Die 



1 ' Beitrage zu einer Eevision der Ammoniten des Schwabischen Jura' pt. ii 

 (1896) p. 146. 



2 ' Ammonites jurensis,' Geol. Mag. 1892, p. 260. 



3 ' Beitr. Rev. d. Aram. d. Schwab. Jura ' pt. ii (1896) p. 166 & pi. xii, fig. 8. 

 Q. J. G. S. No. 241 . l 



