74 BULLETIN OF THE 



Amioceras incipiens Htatt. 



Loc. Semur; Coll. Boucault. 



Sides convex. Pila- with prominent geniculae. Abdomen obtusely an- 

 gular ; keel prominent, narrow; channels either absent or well defined by 

 shallow, narrow depressions. Young, smooth as in Amioceras cuneiformis t 

 but the pilae begin with a line of abdominal tubercles, which quickly 

 spread into true pilas. 



Amioceras semicostatum Hyatt. 

 Loc. Semur ; Coll. Boucault. 



Sides convex. Pilse have square prominent geniculae. Abdomen flat- 

 tened. Keel may be a depressed ridge without channels, prominent 

 without channels, or prominent with well-defined narrow channels ; in 

 the fust variety the young retain the smooth character until a later period 

 than in the second and third. 



Amioceras kridiforme Hyatt. 



Amm. hridion D'Orb., Terr. Jurass., I., p. 205, pi. 51. 



Loc. Whitby, Adnet, Semur ; Coll. Prof. Bronn, Dr. Krantz, and M. 

 Boucault. 



This species differs from A. semicostatus in the larger number and nar- 

 rowness of the whorls, and the prevalence of the deeply channelled variety. 

 The rihs of the young are not as smooth as in Am. semicostatus, and 

 they are developed at an earlier period. 



It differs also from Amm. hridion Ziet., in the absence of tubercles, and 

 its contracted abdomen. 



Amioceras tardecrescens Hyatt. 



Amm. tardecrescens Hauer, Die Ceph. d. Lias d. Nordbstlichen Alpen, 

 p. 20, pi. 3. 



Loc Durrenberg, Ravensberg, Hildesheim, Thionville, and Whitby, 

 Coll. Dr. Krantz, L. de Koninck, and Damon. 



Amioceras ceratitoides L. Agassis, 



Aram, ceratitoides Quens'dt, Die Ceph., p. 239, pi. 19, fig. 3. 

 Amm. cent* Giebel, Fauna der Vorwelt, Ceph., p. 757. 

 Amm. ceras Hauer, Die Ceph. d. Lias d. Nordbstlichen Alpen. 

 Loc. Whitby and Adnet; Coll. Prof. Bronn and Dr. Krantz. 



Amioceras falcaries Hyatt. 



Amm. falcaries Quens'dt, Der Jura, p. 70, pi. 7, figs. 6, 7. 

 Loc. Bonnert, Semur, Raidwangcn, and Basel; Coll. L. de Koninck, 

 Boucault, Mus. of Stuttgart, and Prof. Bronn. 



