1874.] 27 [Hyatt. 



Deroceras desinodum. 



This species is not a member of this series at all, but genetically- 

 allied with the armatus series. 



Androgynoceras hybridum. 



This species is very commonly confused with the other forms of 

 Androgynoceras and Liparoceras by all German authors. It is, 

 however, quite readily distinguished by the large size which it attains 

 before acquiring the peculiar tuberculated lateral and divided ab- 

 dominal pilse of the group to which it belongs. Sowerby's collection 

 shows that his Henleyi was identical with this species, and not 

 with the species which now universally goes by that name. 



Androgynoceras appressum. 



This is quite a distinct form, but is equal to Amm. striatus evolutus 

 Quenst., and to a part of Amm. hybrida Oppel, and appears to lead 

 into a peculiar keeled form, also part of Amm. hybrida Oppel. 



This form becomes almost smooth in the young, and thus resembles 

 Amm. polymorpTius lineatus , which both Quenstedt and Oppel con- 

 sider connected with it. I think the resemblance is caused merely 

 by a mode of development which has the same relation to the mode 

 of development in And. appressum that the mode of development in 

 Bechii has to Henlyi. That is, the young are smooth for a long time 

 in both, and both skip the latsecostan stage, but the adults differ in 

 the subsequently developed characteristics of the adult abdomen. 



Liparoceras indecisum. 



This form has two varieties, one in the collection of the Museum of 

 Comparative Zoology, which in the young approximates quite closely 

 to the young of And. hybrida, and one form in the Munich collection, 

 which is intermediate between the normal forms and the true Hen- 

 leyi] that is, the young have the lataecostan abdomen for a much 

 more limited time. 



Liparoceras Henleyi. 



This is undoubtedly, as Oppel states, only a form of Bechei, but if 

 we join this and Bechei under one name, we must also, according to 

 the same rule, join all the forms from Microceras latcecosta to Bechii 

 inclusive under one specific name, with numerous varieties. 



Liparoceras Bechei. 



This occurs in Lias y with Henleyi and appressum, but the extreme 

 forms are mostly found in Lias a. Sowerby's original is the form 

 usually identified as Bechei, with smooth young. 



