CEPHALOPODA. 



99 



No. 196. Ammonites cordatus, Sow. 



These young shells show the cordate keel from which 

 the specific term is derived, and which assigns the species 

 to the group "Amalthei." From the Middle Oolite at Viel 

 St. Remy. France. 



No. 197. [484, Cast]. Ammonites cordatus, Sow. 



Internal cast of the adult shell showing the foliations. This 

 species varies in size, among adult individuals, from one to eight 

 inches in diameter. From the Oxford Clay (Middle Oolite), Cal- 

 vados, France, and now in the Ward Collection, University of 

 Rochester. Diameter, 7. 



No. 198. [486, Cast]. Ammonites coronatus, Brug. 



This species from the Middle Oolite, very much resembles A. gigas, Ziet, of 

 the Upper Oolite. It is the type of Von Buch's group "Coronati." From 

 Villere, France, and now in the Ward Collection, University of Rochester. 



No. 199. [488, Cast]. Ammonites cornucopise, d'Orb. 



This elegant Ammonite very closely resembles A. fimbriatus, Sow. , but is 

 considered by d'Orbigny a distinct species. Its several whorls are coiled quite 

 loosely, and taper very rapidly towards the center of the shell. From the 

 Upper Lias, Verpilliere, France, and now in the Ward Collection, University 

 of Rochester. Diameter, 12. 



No. 200. Ammonites communis, Sow. 



This species is very frequently found forming the central nucleus of discoid 

 concretions of slaty limestone. These concretions owe their origin to the 

 attracting and cementing power of the decomposing mollusk. From the 

 Upper Lias, Whitby, England. 



No. 201. [490, Cast]. Ammonites fimbriatus. Sow. 



This species is characteristic of the group 

 "Fimbriati." The specimen shows the orna- 

 mental characters of the external shell. The 

 lines of periodical enlargement or growth are 

 very marked on this shell. From the Middle 

 Lias, Charmouth, England. 



