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



Baculites incurvatus Dujardin as figured by Schl titer 1 is a closely re- 

 lated form, that occurs iu the "Emscher Mergel" of Germany. Sev- 

 eral of its associates are considered identical with forms that are found 

 in the Austin limestone and in the upper part of the Colorado forma- 

 tion. 



AMALTHEIDvE. 



Genus BUCHICERAS Hyatt. 



BUCHICERAS SWALLOVI Shumard (sp.). 



PI. xxxvn, Fig. 1; PI. xxxvin, Figs. 1-3. 



Ammonites swallovi Shumard, 1860, Trans. St. Louis Acad. Sci., vol. I, p. 591. 



JBuchiceras swallovi White, 1876, U. S. Geog. and Geol. Sur. West 100th Meridian, vol. 

 iv, p. 202, PI. xx, Figs, la, &, c. 



Compare Placenticeras (perizianum ? var.) liardense Whiteaves, 1889, Cont. to Can. 

 Paleont., vol. I, pt. 2, p. 158, PI. xx, Figs. 1 and 2. 



Dr. White's description of the Utah fossils referred to this species is 

 as follows : 



"Shell moderately large, flattened- discoid; sides greatly convex; 

 dorsum [abdomen] narrowly flattened, the flattened space bordered on 

 each side by a row of more or less distinct nodes ; volutions three or 

 four, partially embracing; umbilicus broad, its outline not clearly 

 defined; deep for so discoid a shell, although it has a shallow aspect 

 because of its breadth and want of definite outline, and exhibiting a 

 large part of each of the inner volutions ; aperture subovate in outline, 

 its longest diameter directed from the center of the shell, narrowest at 

 the outer end, where it is truncated by the flattening of the dorsum 

 [abdomen]; sides of the volutions marked by prominent, somewhat 

 flexuous, rounded costae, extending from the inner to the outer edge; 

 the space between each two of these principal costse is occupied by one 

 or two short ones which do not reach the umbilicus, but they end at the 

 dorsum [abdomen] like the others; upon each costa, near its dorsal 

 [abdominal] end, there is an obtuse node, which, together with the dor- 

 sal [abdominal] nodes before mentioned, constitute a double row of nodes 

 at each side of the dorsum [abdomen]. Saddles all broader, and sim- 

 pler in outline than the lobes, none of the former being really digitate, 

 and those near the ventral side of the volutions are nearly as simple in 

 outline as they are in Ceratites. 



" This shell presents some differences from the description by Dr. 

 Shumard of A. swallovi, the principal of which is the absence of the 

 nodes at the umbilical side of the volutions and of the distinct trans- 

 verse ribs of the dorsum [abdomen] mentioned by him; but these are 

 not regarded as essential specific characters. 



1 Palaeontographica, Vol. XXIV, PL 39, Figa. 6 and 7. 



