104 EOCENE MOLLUSC A. 



The upper part of the hinge-line is nearly straight, which gives a small shoulder to the 

 shell on each side. Trigonoccelia granidata, Nyst, ' Coq. foss. Belg.,' p. 241, pi. 19, fig. I, 

 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 Belcheri, 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 scalaris, J. Sowerby. Tab. XVII, fig. 9, a, h. 



Pectunculus scalabis. J. Sow. Min. Conch., t. 472, fig. 2. 



— — Morris. Catal. Brit. Foss., p. 207, 1854. 



Spec. Char. Testa or biculatd, convexd, inaquilaterali obliqud ; radiatim costulatd, et 

 concentrice striata, decussatd ; costulis granulatis, angustis, separates ; cardine obliquo ; 

 umbonibus parvis ; marginibus crenulatis. 



Shell orbicular, convex, inequilateral, oblique, radiatedly costulated and decussated by 

 lines of growth ; rays rough, subgranular ; hinge oblique ; umbones small ; margins 

 crenulated. 



Diameter, fths 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 costae, 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 deletus. " 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. 



TRIGONOCCELIA. Deshayes. 



Generic Character. Shell equivalve, generally small, inequilateral ; more or less trigo- 

 nular or deltoidal; pedi-lateral margin rounded, siphon i-lateral angular; umbones pro- 

 minent, ventral margin smooth ; hinge-line divergent, with sharp and generally angular 



