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



last turn more than half the entire length; suture well denned in con- 

 sequence of the convexity of the whorls; aperture narrow, equaling 

 about two-fifths the entire length of the shell, angular behind and nar- 

 rowing below to a small, sharply defined notch at the base of the trun- 

 cated columella, which seems to bear two small folds near its lower 

 part, one being formed by the twisted and truncated lower margin ; 

 inner lip a little thickened ; surface ornamented by distinct, regular 

 vertical folds that are nearly or quite obsolete on the body- volution 

 below its upper part, and regular revolving lines quite well defined on 

 the body- turn, especially its lower part, and appear to be obsolete on 

 those of the srjire; lines of growth moderately distinct. 



" Length, 0.50 inch 5 breadth, 0.20 inch; angle of spire, about 30°. 



" This species differs even more strongly from the last [A. gregaria] 

 than that form does from the species rhomboides, having a much more 

 elevated spire and a proportionally smaller body- volution and aperture. 

 In ornamentation, however, the three forms are much alike. The spe- 

 cies here under consideration shows a somewhat more thickened inner 

 lip than I have yet seen in either of the others." 



The fossils from southern Utah that have been referred to Admetopsis 

 gregaria (see last two references above) seem to belong here, if the more 

 slender elongate form can be regarded as a specific character. 



Locality and position. — Near the base of the Cretaceous section at 

 Coalville, Utah, and at several localities in southern Utah. 



Admetopsis humerosa n. sp. 

 PI. xxxiii, Figs. 4 and 5. 



Shell small, slender, fusiform; whorls about eight, the earlier ones 

 rounded and marked by numerous distinct transverse costas, the last 

 two or three distinctly shouldered and smooth. The transverse orna- 

 mentation is proportionately strongest near the apex of the spire, and 

 is gradually reduced as the whorls become shouldered or channeled, 

 until it disappears entirely on the body whorl, and usually on the pre- 

 ceding one. Some specimens show very faint revolving lines. 



Aperture showing the characteristic features of the genus as in the 

 other described species. Inner lip considerably thickened ; outer lip 

 not complete in any of the specimens. 



Length of an average specimen, 15 rara ; breadth, 8 mm . 



This species may be easily distinguished by the shouldered character 

 and smooth aspect of the larger whorls. 



Locality and position. — Near Iron city, southwestern Utah, where it 

 is associated with Glauconia coalvillensis, Barbatia micronema, Corbula 

 nematophora, and other species of the Colorado formation. About 40 

 specimens were collected. 



