ON THE NEW GENtTS OF BIVALVE. 



Our next figure shows the nature of the teeth. 



103 



FIO. in.- INTERIOR OP LEFT VALVE, SHOWING THE TEETH OF THE HINGE. 



The Shell is about two inches long, and a little more than 

 an inch deep, it is distinguished by its peculiarly incurved 

 umbones, and its finely striated external markings. 



This shell was first discovered at Half-way House in a thin 

 bed of ferruginous marl, which separates the so-called zones of 

 Sowerbyi and Humphresianus beds. 



A similar bed occurs in Gloucestershire, separating what we 

 had distinguished as the Trigonia (upper) and Gryphite grits 

 (lower beds). 



This thin band is remarkable both in Dorsetshire and Glouces- 

 tershire for peculiar fossils, among which we may now reckon 

 the Curvirostrum. 



Wo have as yet only found it in Dorsetshire a single speci- 

 men from Bradford Abbas, the same from Half-way House, 

 while several specimens have been obtained from a quarry on 

 Wyke Farm, and it is not uncommon at Louse-hill Quarry. 

 These are stations in Dorsetshire, but it has been found at East 

 Coker, in Somersetshire, in a similar position to that of the 

 Dorset beds. 



