104 EOCENE MOLLUSCA. 
The upper part of the hinge-line is nearly straight, which gives a small shoulder to the 
shell on each side. Triyonocelia granulata, Nyst, ‘Coq. foss. Belg.,’ p. 241, pl. 19, fig. 1, 
strongly resembles our shell by figure and description ; but M. Deshayes, who, I presume, 
has examined the Belgian fossil, says it is specifically different. The artist has given 
rather too much obliquity to our figure. 
Limopsis Belchert, Adams and Reeve, is said by Mr. Jeffreys, ‘Ann. and Mag. Nat. 
Hist.,’ 2nd ser., vol. x, p. 345, Nov., 1862, to be the same as the Eocene species. 
2. Limopsis scauaris, J. Sowerby. Tab. XVII, fig. 9, a, 4. 
PecTUNCULUS scALARIS. J. Sow. Min. Conch., t. 472, fig. 2. 
— — Morris. Catal. Brit. Foss., p. 207, 1854. 
Spec. Char. Testa orbiculatd, convead, inequilaterali obliqud ; radiatim costulatd, et 
concentrice striata, decussatd ; costulis granulatis, angustis, separatis; cardine obliquo ; 
umbonibus parvis ; marginibus crenulatis. : 
Shell orbicular, convex, inzequilateral, oblique, radiatedly costulated and decussated by 
lines of growth; rays rough, subgranular; hinge oblique; umbones small; margins 
crenulated. 
Diameter, :ths of an inch. 
Locality. Barton. 
This is an abundant shell at Barton, where the two valves are often found united. The 
exterior of this species is prettily ornamented with about twenty-four or twenty-six pro- 
minent rays, or rather acutely angular cost, with often an intermediate ray, sometimes 
two; these rays are cut or crossed by prominently rounded ridges of growth, which 
decussate the surface, and produce a nodulous appearance on the rays, like the exterior of 
Pectunculus deictus. “The transverse lines between the ribs resemble the steps of a rope- 
ladder.’ —/J. Sowerby. The hinge-margin is furnished with about five to eight prominent: 
teeth, placed at nearly right angles to the hinge-line on the pedal side, and about nine 
to twelve in a curving direction on the other. The interior of the entire margin is 
irregularly denticulated, but not at the extreme edge. The triangular fossette in the 
area of connexus is large and deep, diverging from the umbo at nearly a right angle. 
TRIGONOCGLIA. Deshayes. 
Generic Character. Shell equivalve, generally small, inequilateral ; more or less trigo- 
nular or deltoidal; pedi-lateral margin rounded, siphoni-lateral angular; umbones pro- 
minent, ventral margin smooth ; hinge-line divergent, with sharp and generally angular 
