Logan.] The Invertebrates, Niobrara Group. 489 



removed without endangering the specimen. For this reason 

 I have not been able to determine the general character of the 

 exterior of the shell. From the smooth condition of the in- 

 terior, it seems there are no ridges or undulations such as mark 

 a majority of the species of this genus. Aside from the condi- 

 tion of the hinge and this apparent lack of ridges and the 

 almost total want of convexity, it most closely resembles Ino- 

 ceramus deformis, but has not the thickness of test of that species. 

 The above specimen was collected from the upper chalk beds 

 ( Hesperornis beds) of Gove county. Fragments of the shell, 

 especially of the hinge, are abundant in these beds, but whole 

 specimens are rare. 



Inocevamns brownii Cragin. 



Inoceramus brownii Cragin, Cont. to the Paleontology of the Plains, Bull. 

 Washb. Coll. Lab. Nat. Hist., 1889. 



Original description: "Shell large, fibrous, equivalve, in- 

 equilateral, short, broad, elevated, and concentrically ribbed 

 and striate ; valves boat -shaped, or unevenly pear-shaped in 

 exterior view, posteriorly shouldered, depressed on the summit 

 of the umbonal region ; beaks obtuse, incurved, closely approxi- 

 mated, their cavity capacious, hinge line more or less angulated 

 between the beaks, provided with numerous transverse cartilage 

 grooves ; interior of shell bearing, on the distal part of the um- 

 bonal cavity (in the right valve at least), several large, com- 

 pressed teeth ; ribs of the shell six or eight on each valve, 

 prominent rounded, broadening from their origins toward the 

 convexities of the valves, more or less folded, grooved, and 

 striated in the direction of their course. 



"Dimensions: Height, eight and one-half inches; breadth 

 (distance between greatest exterior convexities of valve), eight 

 inches; approximate length (greatest anterio-posterior diame- 

 ter measured parallel to hinge line), six inches; thickness, 

 mostly thirteen-hundredths to twenty-five hundredths of an 

 inch. The exterior of the type specimen is more or less studded 

 with the inferior valves of Ostrea congesta, but much less thickly 

 than is usual with the common, large Inocerami of the Niobrara. 



