104 



MOLLUSCA. 



No. 324. Ammonites Rothom.agensis, Brong. 



This is the the type of the group "Rothoinagenses," the members of which 

 are characterized by having a series of tubercles along the dorsal line in place 

 of a keel, They belong chiefly to the Cretaceous period. From the Lower 

 Challf, Dover, England. 



No. 325. [530, Cast]. Ammonites Rothomagensis, Brong. 



An internal cast of part of one whorl, showing the foliations. From the 



same locality, and now in the Ward Collection, University of Rochester. 



Diameter, 7. 

 No. 226. Ammonites semisulcatus, d'Orb. 



From the Cretaceous, Drome, France. 

 No. 227. [531, Cast]. Ammonites serpentinus, Schloth. 



This is the type of the group ''Faldferi," 

 which have a compressed shell with sharp 

 keel. The folds of the shell are numerous, 

 and usually bend with an abrupt curve in 

 the middle of their course. From the 

 Upper Lias, Charmouth, England. 



Diameter, 7. 



No. 228. Ammonites splendens, Sow. 



This variable Ammonite, is a characteristic fossil of the Gault (Cretaceous), 

 Folkestone, England. 



No. 229. [1303, Cast]. Ammonites tornatUS, Brown. 



This Ammonite belongs to the group " globosi," characterized by being very 

 closely coiled, umbilicus quite small or wanting, surface smooth or feebly 

 striated, and devoid of ribs and tubercles. It is from the Trias at Hallstadt, 

 Austria, and is now in the Ward Collection, LTuiversity of Rochester. 



No. 230. Ammonites Woollgari, Mant. 



This species is one of the most 

 marked forms in the group "Rotho- 

 magenses." It has much resemblance 

 to A. Boihomagensis, particularly in 

 the young stage; but differs from it 

 by having less closely coiled whorls, 

 and the ribs fewer, more salient, 

 and more angular on either side of 

 the dorsal plane. From the Creta- 

 ceous of Smith's Branch, Texas. 



No. 231. Ammonites. 

 Polished Section, showing the septa. From the English Lias. 



