1874.] 29 [Hyatt. 



Appendix to Communication on " The Non Reversionary 

 Series of the Liparoceratid^e," etc. 



(Proceedings, Jan. 17th, 1872.) 



Deroceras armatum. 



I have noted that a well preserved specimen of this species occurs 

 in Prof. Fraas' collection from the Raricostatusbed of the Lower Lias. 

 Deroceras alternum. 



This may be a broad whorled variety of Deroceras Zitteli (sp. 

 Oppel), and Deroceras minatum Hyatt, Bull. Mus. Comp. Zool., 

 No. 5, p. 94, is probably the typical variety of the same species fig- 

 ured by Oppel in the Mittheilungen, pi. 42. 



Both of these forms probably came from the Margaritatusbed, 

 though the latter is labeled Upper- Lias, Plateau de Larzac. 



D. alternum approximates to Oppel's species in possessing a large 

 abdominal cell, but the lateral cells and lobes are quite different. 

 These differences are not important, however, and alternum appears 

 the same as Oppel's species; but whether minatum is or not cannot 

 be decided on account of the label referred to above. 

 Deroceras Davcei. 



The Amm. planarmatus of Quenstedt appears to be a form of this 

 species. A specimen in the Museum of Stuttgart is much stouter 

 than the ordinary form of Davcei, but is more nearly allied to that 

 species than the fragment figured and described by Quenstedt. This 

 has no spines and the pilse are split into several upon the abdomen 

 according to Quenstedt's description, though the figure shows that 

 they are merely the abdominal remnants of pilas whose lateral por- 

 tions have been obliterated. This, the absence of tubercles and the 

 fold-like character of the pilse, appear to indicate an old age form of 

 Davoei. I say this with great doubt, because the septa are slightly 

 different, and I have not seen Quenstedt's original specimen. 

 Deroceras muticum. 



This description includes a broad form, which is the Deroceras 

 Venarense (Opp. Spec. Mittheil., pi. 42), and a compressed variety 

 which is named Amm. muticus by Boucault. The specimens are from 

 Venarey, and doubtless are merely varieties of Venarensis, but they 

 agree quite closely with D'Orbigny's figure of Amm. muticus. Un- 

 fortunately the original specimen was not found in D'Orbigny's col- 

 lection, and I think it would be more consistent with prudence to 

 adopt Quenstedt's and Oppel's conclusion, that Amm. muticus D'Orb. 



