14 THE 



only very slightly biplicated, as represented in figure 14. They 

 occur with it, and are commoner. 



6. TEREBRA.TULA DORSOPLANA, Waagen. 



1867. TEREB. DORSOPLAXA, Waagen, Geogn. Paliiont. Beitrlige 

 plate xxxi. (8), figure 7. 



A rather strongly biplicated species, which might, at first 

 sight, be taken for the young of Tereb. perovalis, but which is 

 really easily separable. It has a medium sized rounded fora- 

 men, and its beak ridges are slightly produced near the beak, 

 and then thrown back as it were, thus giving to the shell on 

 each side of the beak a peculiarly folded appearance. Another 

 distinction is the well marked carina down the middle of the 

 larger valve, beginning at the beak. Its valves are always more 

 or less thickened at their junction, both at the sides and base of 

 the shell. These characters are slightly modified in some of the 

 broad specimens. Waagen says that it differs from Tereb. infra- 

 oolithica, E. Desl., on account of the keel down the middle 

 of the larger valve. Our specimens are certainly far larger 

 than those figured by Dr. Waagen, and are from the zone of 

 Murchisonae. He quotes it from the Sowerbyi zone; but I 

 have not yet found this species there. Our specimens would 

 seem to stand in shape, etc., between Tereb. infra-oolithica and 

 Tereb. perovalis. The characters that I have mentioned above 

 will well distinguish it from Tereb. perovalis, specimens of which 

 are found in the same bed with it. Tereb. dorsoplana is rather 

 uncommon, and I only know of two places where it has occurred 

 in this district. 



Localities. Marston-road and near Sherborne (Dorset). 

 Waagen quotes it from Gingen (Wiirtemberg), Gunsberg (Canton 

 Solothurn), and La Hoche Pourrie, near Salins (Jura). 



Dimensions. Length 1 inch 4 lines, breadth 1 inch 3 lines, 

 depth 10 lines. Another Specimen. Length 1 inch 6 lines, 

 breadth 1 inch 3 lines, depth 10 lines. Of a Broad Specimen. 

 Length 1 inch 7 lines, breadth 1 inch 7 lines, depth 1 1 lines. 



