JDEASSIG PERIOD. . 167 



numerous, distinct, slightly-raised, concentric lines or narrow folds, which 

 meet at nearly right angles at the umbonal ridge. 



Height, about eight millimeters ; length, eight and a half millimeters. 



Position and locality/. — Strata probably of the Jurassic "period ; Camp 

 Cottonwood, old Mormon road, Nevada. 



Genus TEIGONIA Bruguiere, 1789. 



Trigonia (?). 



Associated with Camptonectes heUistriatus Meek and Hayden at a locality 

 five miles east of Gunnison, Utah, some imperfect examples of a species of 

 Trigonia of Jurassic type were found. They are too imperfect for specific 

 recognition, but are noticed here in consequence of the value of the type in 

 stratigraphic geology. 



Class GASTEROPODA. 



Subclass DKECA. - 



Order RHIPHIDOGLOSSA. 



Suborder PODOPHTHALMA. 



Family NERITID^. 



Genus NERITINA Lamarck, 1809. 



Neritina? phaseolaris Wbite. 



Plate XIII, fig. 1 a, h, e, (7, nm\ c. 



Neritina phaseolarisWhite, 1874, Expl. & Surv. west 100th Merid., Prelim. Hep. Invert. 

 Foss., 24. 



Shell small, obliquely suboval ; volutions apparently from two and a 

 half to three, the last one composing all but a very small part of that portion 

 of the shell which is exposed to view ; aperture obliquely ovate ; character 

 of the inner lip not clearly made out, but. the shell has the external aspect 

 of Neritina ; a small elevated fold is usually seen at the suture upon the 

 outer volution appressed against the next volution within. In some examples, 

 the convexity of the outer volution, from the base of the small elevated fold 

 above to the margin of the aperture below, is quite regular ; but, in other 



