170 DESCRIPTION OF SHELLS. 
Pectunculus globosus. (Tab. III. fig. 20.) 
Spec. Cuar.—Subglobose, with a small posterior lobe, smooth and nearly 
even; hinge-line arched with about twenty large teeth ; muscular impressions 
deep, the posterior one round, the other ovate; margin irregularly circular, 
toothed. 
A well-defined irregularly heart-shaped species. I have a foreign specimen 
precisely resembling it, but not named, I therefore presume it to be unde- 
scribed. 
Nucula serrata. (Tab. II. fig. 9.) 
Spec. Cuar.—Transversely ovate, elongated ; ornamented with many reflected 
concentric plates or ridges, which form teeth upon the edge of the anterior area, 
which is very narrow, smooth, and has in each valve a ridge along its middle ; 
beaks central ; anterior extremity pointed, elongated. 
About twice as long as high. 
In the Cabinet of Mr. Edwards. 
Nucula bisulcata. (Tab. I. fig. 13.) 
Spec. Cuar.—Elliptical, compressed, smooth ; anterior extremity angular ; 
posterior slope marked with two deep longitudinal furrows in each valve ; beaks 
near the anterior extremity ; teeth in the anterior portion of the hinge five 
or SIX. 
Height and length as 8 to 13. 
A handsome species well characterized by the furrows in the large posterior 
slope. From the Cabinet of Mr. Edwards. 
Limopsis granulata. (Tab. III. fig. 19.) 
Limopsis is a genus distinguished from Pectunculus by a triangular pit in the 
hinge between the two sets of teeth. It was named Trigonocelia by Galeotti and 
Nyst in 1835, but we are informed that the name Limopsis given by Sassi has 
the priority. 
The shell before us is a remarkable instance of the difference between the Bar- 
ton and Bracklesham beds, and the similarity of the latter to those of Grignon ; 
for this is the same species that occurs at Grignon, while another species of the 
