498 GEOLOGICAL SURVEY OF THE TERKITORIES. 



ill outline at the middle, nnd i)rovided with a slij^ht projection on each 

 side, but not proi)eiiy cienate or dentate; outer lii) rather thi(;k, obtuse, 

 nearly or (|aite sniooth, and eontinuou.s around the margins with the inner 

 one; a[)erture small, and transversely semicircular. Surface i)Oiished 

 and ornamented by fifteen to twenty light yellowish or cream-colored, 

 simi)le radiating costa\ separated by shallow, bright brownish furrows 

 of about the same breadth ; lines of growth moderately distinct.* 



Length, 0.31 inch ; breadth, 0.25 inch ; convexity, 0.12 inch. 



I am in some doubt in regard to the proper disposition to make of 

 tliis little shell. In most of its cliaracters it seems to conform pretty 

 nearly with Dostia of Cxi'ay, generally regarded as a subgenus under Neri- 

 tina, Lamarck, {^=¥eriteUa, Humphrey.) It has a much smaller and less 

 promineut spire, however, and a more convex and broader inner lip, 

 than, the type of that group, and also wants the crcnulations of the 

 inner lip seen in the same. In its limpet-like form, tumid, greatly de- 

 veloped inner lip, and minutely coiled apex, it approaches Vclates, Mont- 

 fort; and I am not quite sure that I would not be nearer right to call 

 it VclaicH bellatula. Still it diflers from the typical form of that genus 

 in having its apex depressed to the posterior margin, instead of being 

 elevated and nearly central; while the margin of its inner lip wants the 

 distinct denticulations seen in that of that shell. 



Of course, if Humphrey's catalogue genera are, to be adopted, oq 

 account of their priority of date over those of Lamarck and others that 

 were accom})anied by diagnoses, the name of this shell, sup])osing the 

 view here adoi)ted in regard to its affluities to be correct, would become 

 Neritella flJostiaJ bellatula. 



Locality and position. — Carleton's coal-mine, Coalville, Utah. 



Neritina (Dostia f) patelliformis, Meek. 



Shell small, thick, oval or subelliptic; nucleus nearly posterior and 

 generally more or less elevated above the posterior margin, but always 

 lower than the mid<lle position of the dorsal region in front of it, 

 directed obliquely backward, and, in well-preserved specimens, minutely 

 subspiral at the immediate more or less oblique apex; inner lip very 

 broad, or having the form of a thick, smooth, convex septum, that 

 extends forward more than half the length of the shell ; outer lip thick- 

 ened, obtuse, and smooth within ; open part of the aperture small and 

 transversely semicircular. Surface with moderately distinct lines of 

 growth. 



Length of one of the largest specimens found, 0.G2 inch; breadth, 

 0.50 inch ; height or convexity, 0.33 inch. 



This torm is evidently very nearly related to the last, and may possi- 

 bly be a more robust variety of the same. It attains a much larger size, 

 however, than any of the specimens of that shell I have seen, and pre- 

 sents a more elevated form, with a thicker and more tumid inner lip; 

 while its nucleus is often more elevated above the margin, though not 

 always so. At first, I thought the absence of radiating costa3 on this 

 shell would very decidedly distinguish it from the last, but on farther 

 examination I find the costse almost obsolete on one of the specimens 

 of that species, though the bright brown color of the spaces between 

 them makes the lighter interspaces quite apparent. Among the speci- 

 mens of the larger form under consideration, (broken directly from the 



* Of course the colors nientiouecl are not known to present the same tints in the fossil 

 Bhells that ornamented them when the animal was alive. 



