18 GEOLOGICAL SURVEY OF THE TERRITORIES. 
east of the Rocky Mountains. The type specimens were obtained from 
Fossil Ridge, about 16 miles westward from Greeley, and about 6 miles 
southward from Fort Collins, Col. The best examples yet discovered, 
one of which is figured on plate 11, were obtained at that locality by Mr. 
A. Lakes, by whom they have since been sent to Princeton College, New 
Jersey. 
Genus VOLSELLA Scopoli. 
Subgenus BRACHYDONTES Swainson. 
VOLSELLA (BRACHYDONTES) MULTILINIGERA Meek, 
Plate 11, fig. 3 a. 
Modiola bs Meek (not Remer), 1871, An. Rep. U. 8S. Geol. Sur. Terr. for 1870, 
Dp. 207. 
Modiola (Brachydontes) multilinigera Meek, 1873, An. Rep. U. 8. Geol. Sur. Terr. for 
1872, p. 492. 
In a catalogue of Cretaceous fossils, published in the Annual Report of 
this Survey for 1870, Mr. Meek (loc. cit.) referred this species to the 
Modiola pedernalis of Roemer, but he afterward gave it the new specific 
name as above, together with the following description and remarks : 
‘‘ Shell rather above medium size, obliquely arcuate-subovate ; valves 
strongly convex along the umbonal slopes, thence cuneate posteriorly 
and abruptly curved inward below the middle in front; posterior margin 
‘forming a broad, regular convex curve from the end of the hinge down- 
ward to the anterior basal extremity, which is very narrowly and ab- 
ruptly rounded; anterior margin ranging obliquely backward and down- 
ward to the narrow basal extremity, and strongly sinuous along the 
middle, above which it projects more or less beyond the umbonail ridge, 
so as to form a moderately prominent, somewhat compressed, protuber- 
ance; hinge margin nearly or quite straight, ranging at an angle of 50° 
or 60° above an imaginary line drawn from the beaks to the most prom- 
inent part of the basal outline, and equaling about one-half the greatest 
oblique length of the valves; beaks nearly terminal, rather compressed, 
very oblique, and scarcely rising above the hinge margin; umbonal slopes 
prominent and more or less strongly arcuate. Surface ornamented with 
fine lines of growth, crossed by regular radiating lines that are very fine 
and crowded on the anterior part of the valves, but become coarser above 
and behind the umbonal ridge, the largest being near the dorsal side, 
where they bifurcate so as to become very fine, and curve more or less 
upward before reaching the cardinal margin. 
‘Greatest length, measuring from the beaks obliquely to the most 
prominent part of the basal margin of a large specimen, 1.90 inches ; 
greatest breadth at right angles to the same, 1 ineh; convexity, 0.76 
inch. 
‘““On first examining some imperfect casts of this shell brought by 
Dr. Hayden from near Coalville, Utah, I was led to think it probably 
the form described by Dr. Roemer from Texas under the name Modiola 
pedernalis, to which I referred it provisionally in making out the list of 
Cretaceous fossils for Dr. Hayden’s report for 1870. Further compari- 
sons of better specimens collected at the same locality during the past 
summer, however, have satisfied me that it presents well-marked and 
constant differences from the Texas shell. In the first place it is dis- 
tinctly more arcuate, so much so that when placed with its hinge line in 
a horizontal position, the outline of its posterior margin, instead of form- 
