5:20 v errucid.e. 



locality — but I am much surprised from the general distri- 

 bution of the species, that V. Stromia should occur in so 

 distant and isolated an area. After careful examination, I 

 can discover no constant difference between the Red Sea 

 and British specimens. 



The specimens from the Crag have not their moveable 

 opercular valves, which offer much more important diagnostic 

 characters than the shell ; but as far as the latter is con- 

 cerned, no difference whatever can be perceived from V. 

 Stromia. 



2. Verruca laevigata. PL 21, fig. 3 a, 3 b. 



Verruca laevigata. G. B. Sowerby. Genera of Recent and Fossil 



Shells, Plate. 



Moveable scutum, with the lower articular ridge broader 

 than the short upper articular ridge : moveable tergum broader 

 than high, with the upper articular ridge produced into a 

 point. 



Hab. — Tierra delFuego ; Eastern Patagonia, nineteen fathoms ; Chile ; Peru ; 

 Mus. Brit., Cuming, Stutchbury, Darwin: attached to shells, and often to 

 Balanus Iccms and psittacus. 



I can point out no difference in the shell between this 

 species and V. Stromia, excepting that its walls seem in- 

 variably to be smooth, which is rarely the case with V. 

 Stromia; perhaps also the oblique interfolding articular 

 plates between the several compartments are here more 

 prominent. It appears that specimens with the left side 

 uppermost, and therefore with the left opercular valves 

 moveable, are considerably more common than those with 

 the right valves moveable. The moveable scutum and 

 tergum are articulated together by much more prominent 

 articular ridges than in V. Stromia, and the two valves 

 together are broader in proportion to their height, — the 

 height being measured from the apex to the basal margin. 

 In the scutum the lower articular ridge is considerably 

 broader than the short upper ridge. In the tergum, the 



