308 EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



that are regarded as exclusively marine. It appears to be of tlie same 

 general type as Physa carletoni Meek, just described, and may be specific- 

 ally identical, but it is too imperfect to determine tbat point satisfac- 

 torily. Its chief value lies in the proof it affords of the contemporaneous 

 near proximity of land, with its fresh waters containing a moUuscan 

 fauna; and in connecticfu with other facts just recorded, it shows a long 

 continuation of the existence of a shore-hne there. 



The locaUty from wliich this example was obtained is from the high 

 ridge just northeastward from Coalville, Utah. 



Genus NEEITrN"A Lamarck. 

 ISTekitina pisum Meek. 



Plate 7, figs. 11 a, 1), and c. 



Neritina (Neritella) pisum Meek, 1873, An. Eep. U. S. Geol. Surv. Terr, for 1872, p. 500. 



The following is Mr. Meek's original description of this species (loc. 

 cit.), which is copied here, since no additional facts have been obtained 

 concerning its characteristics and afOinities : 



" Shell globose; spire much depressed; volutions about three, increas- 

 ing in size, so that the last or body turn (which is a little depressed 

 above) composes nearly the entire shell; inner lip broad, flattened, and 

 smooth; aperture small and semicircular; surface nearly or quite smooth. 



" Height, 0.22 inch ; breadth, 0.26 inch. 



" LocaUty and position. — Coalville, Utah. Cretaceous ; from below the 

 lower bed of coal." 



It is associated with Weritina pisiformis Meek, W. ( Velatella) patelli- 

 formis Meek (also var. weberensis White), Turhonilla (Chemnitzia) coal- 

 villensis Meek, Turritella eoalvillensis Meek, and Euspira eoalvillensis 

 White. The strata containing these species appear to be from near the 

 top of the Colorado Group, or near the base of the Fox Hills Group. 

 This question cannot be decided satisfactorily, from the fact that the 

 numerous species from all the strata of that interesting locality are 

 mostly unique, and the lithological characteristics are such as to give 

 little aid in the determination of the boundaries of the groups there rep- 

 resented. 



E'eeitina incompta (sp. nov.). 



Plate 7, figs. 6 a, h, and c. 

 Neritina iannisteri (Meek) WMte, 1876, Powell's Eep. Geol. Uinta Mts. p. 98. 



Shell transversely elongate when adult; spire depressed, abruptly 

 convex, smaU, but rising perceptibly above the body-volution; volu- 

 tions three and a half or four, increasing rapidly in size, the last one 

 comprising much the greater part of the shell, regularly convex or with 

 a faint appearance of flattening upon the distal side of the last one ; 

 suture moderately distinct ; aperture rather large, its outer border regu- 

 larly rounded, proximal and distal margins slightly convex and subpar- 

 allel; outer lip thin-edged; inner hp moderately long, plain, slightly 

 concave upon its face, not very broad, sloping inward. Surface marked 

 by ordinary lines of growth. 



Length, in direction of the axis, 12 millimeters ; breadth across the 

 aperture and body-volution, 17 millimeters. 



This species resembles Jfc bannisteri Meek from the brackish-water 



