CEETACEODS PEfilOD. 179 



at right angles with the front of the shell, and only a little oblique witli the 

 axis ; a more or less distinct, but somewhat irregular, furrow extending the 

 whole length of the shell from the posterior side of the umbo to the postero- 

 basal margin, giving each valve an obscurely-bilobed appearance ; crenu- 

 lated face of the hinge narrow, crenulations small ; umbonal region narrow ; 

 beaks prominent, cm-ved forward and inward ; test comparatively thin 

 throughout the whole shell ; surface having the ordinary concentric lines of 

 growth, and the test is also thrown into numerous rude and u-regular con- 

 centric undulations. 



Length of the largest example in the collection, about twenty-two cen- 

 timeters ; greatest breadth, about fifteen centimeters. 



This species is remarkable for the rudeness and extravagant irregu- 

 larity of the undulations of the surface, of which in-egularity the outline also 

 partakes, giving the shell a flaccid aspect. The specimens of the collections 

 are almost wholly in the form of natural casts, being preserved in a fine- 

 grained calcareous sandstone, some of which is crowded with fragments of 

 this species. 



Position and locality. — Strata of the Cretaceous period; five miles above 

 Pueblo, Colorado. 



Inoceramus deformis Meek. 



Plate XV, lig. 1 a and b. 



Inoceramus deformis Meek, 1872, Geol. Surv. Wyoming & Contiguous Territories, 296. 

 Inoceramus deformis Meek, 1874, (Manuscript) U. S. Geol. Expl. 40th Parallel. 



Shell moderately large, irregularly subovate or subcircular in marginal 

 outline ; entire fonu subglobose when adult ; valves subequal, very much 

 inflated ; beaks broad, not very prominent ; hinge-line short ; cardinal bor- 

 der of test somewhat massive ; crenulated face of the hinge moderately 

 broad ; test thin in the middle region of the valves, but it becomes greatly 

 thickened at the margin of old shells, in some cases forming a massive rim 

 around the whole border of each valve, including the cardinal border. 



Surface marked by the ordinary fine concentric lines of growth, and 

 the test is also thrown into more or less regular, coarse, concentric folds or 

 undulations. 



Diameter of the largest example in the collections, measured along the 



