

75 



Young examples, similar to the one figured by Sowerby as tha 

 type of his species, are elongated and moderately biplicated near 

 the front, but with age the shell becomes broader, and is often, 

 although not always so, so much thickened that the biplication 

 disappears. In this last condition we have the variety ampla of 

 Buckman. Sometimes, again, as is the case with some specimens 

 from Cheltenham, the shell, when adult, and of large size, 

 retains the biplication of its valves, and in this state constitutes 

 the variety Kleinii of Lamarck. But when we have before us a 

 large number of specimens we find that these varieties merge 

 one into the other and constitute a single very variable species. 

 The beak is rounded, and truncated by a rather oval-shaped 

 foramen, nearly touching and even sometimes overlying the 

 umbone of the opposite valve. T. perovalis occurs at Bradford 

 Abbas, near Sherborne, Half-way House, and other places. 



No. 2. TEREBRATTJLA STEPHANI, n. sp. Plate I., fig. 3. 



The shells composing this species are more or less sub-pent- 

 agonal, and longer than wide. It does not usually exceed one 

 inch nine lines in length by one inch four lines in breadth. The 

 dorsal or smaller valve is moderately convex, with two prominent 

 folds on the posterior half of the valve. These rounded folds are 

 more or less wide apart, leaving between them a sinus of greater 

 or lesser depth. The larger or ventral valve is a little more con- 

 vex than the dorsal one, with a central longitudinal more or less 

 prominent fold ; the beak is incurved and the foramen but 

 slightly separated from the hinge-line. This is the most abund- 

 ant fossil at Bradford Abbas, Half-way House, Broadwinsor, 

 near Sherborne, and Crewkerne Station. It is intermediate in 

 shape between Ter. Phillipsii and Ter. perovalis, and does not 

 attain to half the size of either of those species. 



No. 3. TEREBRATULA PHILLIPSII, Morris. Plate III., fig. 2, 2a. 



TEREBRATULA PHILLIPSII, Morris. Annals and Mag. of Nat. 

 Hist., vol. xx., p. 255, pi. xviii., fig. 9, 1847. 



Shell elongated, sub-pentagonal, posterior half of the shell 

 tapering ; the beak is perforated by an oval-shaped foramen 



