GEOLOGICAL SURVEY OF THE TEREITOEIES. 503 



spire being somewhat below the middle, where they are angular; sur- 

 face below the angle flattened, or a little concave, and sloping rather 

 abruptly iuward and downward to the suture, while above, to near the 

 upper margin, where there is a shallow revolving concavity a little below 

 the suture, it is convex; hist volutiou probably biangular around the 

 middle; suture well defined; aperture unknown. Surface ornamented 

 by rather obscure revolving ridges, about five of which may be counted 

 on each volution of the spire, one being at the lower margin immediately 

 above the suture; another, whicli is also the largest, occupying the most 

 prominent angular part of the whorl ; and above this three others 

 occur, one being above the revolving concavity, and at the immediate 

 upper margin ; lines of growth obscure and making a strong backward 

 curve in crossing the micldle of the volutions. 



I have not seen specimens of this fine species sufficiently well pre- 

 served to be able to give accurate measurements, though those I 

 have had an opportunity to examine indicate a length of not less than 

 two inches and a fraction, and a breadth of 0.93 inch. The angle of its 

 spire, as taken from near the middle of a large specimen, imperfect at 

 both extremities, measures about 23°, while smaller individuals, com- 

 posed of tive or six of the upper volutions, show an angle of nearly 30°. 

 It is, therefore, evidently a large, robust species, that increases rather 

 rapidly in size from the apex. 



Specimens of this species were brought in by Dr. Hayden a year or 

 two since, and were supposed by me probably to belong to T. Martine- 

 z€7ms^ Gabb, to which it is evidently related in size, form, and general 

 appearance. Since seeing the California State collection, at San Fran- 

 cisco, during the past summer, however, and some additional collections 

 from Coalville, I have become satisfied that the Utah shell is distinct 

 from Mr. Gabb's species. In this opinion Mr. Gabb also concurs, after 

 seeing our specimens. The most obvious dilference is that our shell 

 has the volutions constantly convex above the angle, and below the 

 revolving concavity near the upper part, while in the California species 

 the upper slope of the volutions is regularly concave from the upper 

 margin to the angle. Better specimens would doubtless show other 

 differences. 



Locality and position. — Coalville, Utah. From the Cretaceous, beneath 

 the lower heavy bed of coal. 



TUE-EITELLA SPIRONEMA, Meek. 



Shell rather small, or scarcely attaining a medium size, elongate coni- 

 cal; volutions about fifteen, increasing very gradually in size, mod- 

 erately convex, last one rounded in the middle; aperture apparently 

 ovate; columella rather regularly arcuate. Surface ornamented by 

 squarish, rather regular revolving thread like lines, with nearly equal 

 furrows between ; about five to seven or eight of the lines and furrows 

 are seen on each of the turns of the spire, and nearly twice as many on 

 the body whorl, v>here those below the middle become abruptly smaller 

 and more crowded than those above; lines of growth obscure and gently 

 arched in crossing the volution; suture moderately distinct. 



Length of the largest specimen found, 0.82 inch ; breadth of body volu- 

 tions, 0.23 inch ; spire nearly regular; divergence of its slopes, about 17°. 



There is a slightly polished, appearance of the surface of this shell 

 that is not often seen in the true TurrUellai and gives origin to some 

 doubts whether it may not belong to some group allied to Aclis or Me- 

 nestho. As in size and general appearance, however, it seems to cor- 



