488 H. W. SHIMER PERMO-TRIASSIC OF NORTHWESTERN ARIZONA 



Dielasma bovidens (Morton). — One specimen from the Kaibab Plateau 

 may belong to D. prolongatum Girty from the Gnadalnpian.^ 



Cliothyridina orbicularis (McChesney). — Our specimens agree in gen- 

 eral with the ones figured by White, under the name of Spirigera plano- 

 sulcata Phillips, in the Eeport on the 100th Meridian, volume 4, plate 10, 

 figures 5a-d. 



Plagioglypta carina White. — The surface ornamentation is well shown 

 upon some specimens. There are approximately six rounded, concentric 

 lines in the space of one millimeter. Faint longitudinal striations were 

 also noted upon one or two specimens. Some of the specimens reach a 

 large size, 13 millimeters in diameter — a diameter equal to that of speci- 

 mens from the Lake Minnewanka region of Alberta. 



Euphemus carboimrius (Cox). — With this species are identified speci- 

 mens which are similar in size and general appearance to Cox's type as 

 figured in the 13th Indiana Survey Eeport, plate 33, figures 6-8. They 

 have, however, 15-20 (instead of 20-28) revolving costse. There is no 

 true umbilicus, a shadow depression only being present in this region of 

 the shell. 



E. subpapillosus White was noted by Doctor White from Wild Band 

 Pockets,^ but has failed to make its appearance in our collections. 



Nucula perumbo7iata White. — Our specimens collected from the game 

 locality as White's types are somewhat thinner (that is, measured through 

 the combined valves) than those figured."^ Otherwise they are apparently 

 identical. 



Leda obesa (White). — Our specimens doubtless belong to White's 

 Nuculana obesa originally described from the Wild Band Pockets area. 

 They are similar in shape, size, hinge-line, and surface markings. One 

 internal mold shows that there was a rounded internal ridge extending 

 from the beak in a slight curve posteriorly three-fourths of the distance 

 to the edge of tlje shell. The position of this rather strong internal ridge 

 appears upon the outside of the shell as a faint depression. This depres- 

 sion also occurs in the specimens figured by Girty from the phosphate 

 beds of Wyoming and Idaho. ^ The presence of this internal buttress 

 makes this species approach the genus Cleidophorus. 



Ba'kewellia parva M. & H. — Some of the specimens from the Moenkopi 

 may perhaps have been better identified as Pteria richardsoni, described 

 by Girty from the Guadalupian. Since they are poorly preserved, they 

 are included with the other specimens in this wide-spread species. 



s Op. cit, p. 331, pi. 16, fig. 5. 



«Contrib. to Inv. Paleont., nos. 2-8, p. 138, pi. 34, fig. 3a. 



' Op. cit, p. 136, pi. 34, figs. 7a-6. 



' U. S. Geol. Survey, Bull. 436, p. 40, pi. 4, figs. 7, 8. 



