MUSEUM OF COMPARATIVE ZOOLOGY. 93 



Amm. Vahlani QuensMt, Der Jura, p. 131, pi. 16, fig. 2 - 3. 

 Loc. St. Araand, Semur, Balingen, Rentlingen, and Gagenbcrg ; Coll. 

 Mus. of Stuttgart, L. de Koninck, M. Boucault, and L. Agassiz. 



Tropidoceras * Hyatt. 



Abdomen invariably keeled, much narrower than the dorsal side of the 

 whorl. Pilas single, smooth or tuberculated in the same species, do not ex- 

 tend across the abdomen in any species. 



Young are smooth for one or two whorls. Keel and pila> appear simul- 

 taneously. Septa have a more complicated aspect than in the preceding 

 genus, the minor lobes being deeper and more numerous. The abdominal 

 very broad at the bottom, narrower above. Superior lateral lobe narrow, 

 and about the same depth as the abdominal. Inferior nearly the same, 

 but less branching than the superior lateral. One auxiliary lobe exposed 

 on the side. Abdominal cell very broad. Superior lateral and inferior 

 lateral cells very irregularly divided by minor lobes. One small auxiliary 

 lobe exposed on the 6ide. 



Tropidoceras Actseon Hyatt. 



Amm. Actceon D'Orb., Terr. Jurass., Ceph., p. 232, pi. 61, fig. 1-3. 

 Loc. Semur and Schbppenstadt ; Coll. Dr. Krantz and L. de Koninck. 



Tropidoceras JEgseon Hyatt. 



Amm. JEgceon D'Orb., Terr. Jurass., Ceph., p. 234, pi. 61, fig. 4-6. 

 Loc. Pies de Semur ; Coll. M. Boucault. 



Tropidoceras Masseanum Hyatt. 



Amm. Masseanus D'Orb., Terr. Jurass., Ceph., p. 225, pi. 58. 

 Amm. Masseanus Quens'dt, Die Ceph., p. 90, pi. 5, fig. 2. 

 Loc. Scarborough in Yorkshire, Pres de Semur, and Balingen ; Coll. Dr. 

 Krantz, L. de Koninck, and M. Boucault. 



Upper Lias. 



DISCOCERATIDiE. 



Ophioceras. 

 Ophioceras Levesquei Hyatt. 



Amm. Levesquei D'Orb., Terr. Jurass., Ceph., I., p. 230, pi. 60. 

 Amm. Solaris Ziet, Verst. Wiirt., p. 19, pi. 14, fig. 7. 

 Amm. radians quadralus Quens'dt, Die Ceph., p. 113. 

 Loc. Niort, Salins, Heiningen, and Metzingen ; Coll. Mus. of Stuttgart, 

 Dr. Krantz, and L. de Koninck. 



* Tponls, a keel. 



