178 COLORADO FORMATION AND ITS INVERTEBRATE FAUNA, [bull. 106. 



Prionotropis? lcevianus White (sp.). 



PI. xliii, Figs. 3 and 4. 



Ammonites Icevianu* White, 1876, TT. S. G"eo2. and Geol. Sur. West 100th Meridian, 

 vol. IV, p. 201, PI. 19, Figs. In and 6. 



Original description : 



u Shell moderately large, robust ; volutions four or more, increasing 

 rapidly in size, especially the outer one, so that the umbilicus is rather 

 deep but yet showing all the volutions, each volution embracing be- 

 tween one-quarter and one third of the width of each preceding one; 

 transverse section of outer volution, between the nodes, oval-subquad- 

 rate; surface, upon each side, marked by a row of moderately ele- 

 vated, transversely elongate nodes, situated about one-third of the 

 distance from the umbilicus to the dorsum [abdomen] ; and also by a 

 row of very prominent nodes on each side of the dorsum [abdomen]. 

 Each of these rows consists of the same number of nodes. The dorsal 

 [abdominal] nodes diverge strongly, but are wholly embraced by each 

 succeeding volution, and do not therefore appear in the uihbilicus. 

 Between these two rows of dorsal [abdominal] nodes, the dorsum [ab- 

 domen] is slightly convex, and the outer surface of the shell appears 

 to have been marked by a small median carina. Between these nodes 

 and the umbilicus the sides of the volution are broadly convex. 



"A greater transverse elongation of the lateral nodes than exists on 

 our example would make each continuous with its corresponding dor- 

 sal node, which would give to each lateral pair of nodes the character 

 of a rib. It is not improbable that this modification may be found to 

 exist in some examples of the species. 



" Septa complex; dorsal [abdominal] lobe and part of dorsal [abdom- 

 inal] saddle unknown; superior lateral lobe moderately large, but not 

 bifid; inferior lateral lobe small, narrow, not bifid; accessory lobes and 

 saddles more or less deeply notched or dentate. 



" Diameter of the only example in the collections, the larger part of 

 the outer chamber being broken away, 14 centimeters. 



" Specific name given in honor of Dr. Oscar Lcew. 



" Position and locality. — Strata of the Cretaceous period; Ojo de los 

 Cuervas, New Mexico." 



The type specimen is the only one known that can be positively re- 

 ferred to this species. It is considerably weather-worn on the abdo- 

 men, so that the abdominal lobe of the septum is destroyed, and it is 

 impossible to say whether the shell had a keel or not. The character 

 of the ornamentation and of the septum, so far as it is preserved, sug- 

 gests relationship with Prionotropis woolgari and it is provisionally 

 referred to the same genus. It is considerably more involute than the 

 species just mentioned. 



Ammonites nodosoides, as figured by Schluter, 1 resembles this species 



'Palaeontograpliica, vol. xxi, p. 19, PI. 8. 



