136 COLORADO FORMATION AND ITS INVERTEBRATE FAUNA, [bull. 10* 



belong to Meek's species, especially since many of the associated forms 

 are identical in the two regions. 



The extreme forms represented by Figs. 11 and 14 seem sufficiently dif- 

 ferent to be regarded as distinct species, but there are many interme- 

 diate forms and every character by which they might be separated is 

 variable, consequently I shall include them all under the one name for 

 the present. The most nearly related species with which I am ac- 

 quainted is Gyrodes pctrosa Morton (sp.), from the Eipley formation of 

 the Atlantic and Gulf border regions. 



Locality and position. — In the lower portion of the Cretaceous section 

 at Coalville, Utah, ranging upward to the top of the " second ridge;" 

 abundant in the Pugnellus sandstone at many localities in Huerfano 

 park, Colorado. 



Gyrodes conradi Meek. 



PI. xxix, Figs. 7 and 8. 

 Gyrodes conradi Meek, 1876, U. S. Geol. Sur. Terr., vol. ix, p. 310, Figs. 33-36 in text. 



Original description : 



" Shell obliquely depressed-subglobose, the height being about seven- 

 eighths the breadth ; volutions four to five, increasing rapidly in size, 

 the last one forming about nine-tenths of the entire bulk, rounded on 

 the outer side, somewhat produced and acutely carinated around the 

 middle below, and, like those of the spire, with the truncation of the 

 upper edge moderately broad and a little concave; spire much depressed ; 

 umbilicus very broad and somewhat funnel-shaped, with its marginal 

 angle prominent, acute, and regularly and rather distinctly crenate, 

 while some distance within there is a second less prominent, linear, 

 revolving ridge; aperture sub-rhombic and about twice as high as wide, 

 distinctly angular at the termination of the revolving carina of the 

 under side of the body-volution below, and obtusely angular above; 

 outer lip very oblique, being produced above, and thence nearly straight, 

 and extending obliquely backward and downward to the basal angle, 

 where it connects with the lower extremity of the thin inner lip by a 

 small, sharp sinus, or emargination ; surface nearly smooth, or having 

 obscure lines of growth, that become stronger and show a tendency to 

 gather into little wrinkles on the upper truncated part of the volutions, 

 while on well-preserved specimens the faintest possible traces of fine 

 revolving striae may be seen by the aid of a magnifier. 



"Height, 0.91 inch; breadth, about 1.10 inches; height of aperture, 

 0.86 inch; breadth of same, 0.43 inch.' 7 



Some larger specimens from Huerfano park, Colorado, are propor- 

 tionally somewhat more elevated and have a narrower umbilicus than 

 the type, with which they agree in all other respects. 



This species is very closely related to Gyrodes pansus Stoliczka, from 

 the Cretaceous of southern India, and it may also be compared with G. 

 crenata Conrad, from the Eipley formation. 



