VERRUCA STROMIA. 519 



Ochthosia Stroemia. Ranzani. Memoire di Storia Nat., 1820. 

 Clisia striata. Leach. Encyclop. Brit. Suppl., vol 3 (sine des- 



cript.), 1824. 

 Clitia verruca. G. B. Sowerby. Genera of Recent and Eossil 



Shells, Plate. 

 Verruca Stromii. /. E. Gray. Annals of Philosophy (new series), 



vol. 10, Aug., 1825. 



Moveable scutum, with the lower articular ridge not lialf as 

 broad as the short upper articular ridge : shell generally 

 ribbed longitudinally. 



Var. s with the shell not longitudinally ribbed. 



Hah. — Shores of Great Britain and Ireland, Shetland Islands ; and, ac- 

 cording to various authors, Denmark, Iceland, and shores of northern Europe. 

 Red Sea, Brit. Mus. Attached to shells, laminarise, rocks, crabs, and floating 

 bark, from low tidal mark to fifty or ninety fathoms. 



Fossil iu Glacial deposits of Scotland, Mus. Lyell; Red Crag (Walton, Essex), 

 Coralline Crag (Sutton), Mus. S. V. Wood. 



I have given so full a description of the genus that little 

 remains to be said under the species. Generally the whole 

 shell is covered (independently of the interfolding, oblique, 

 articulating plates) by narrow, longitudinal ridges or folds; 

 and by this character alone the ordinary variety of V. Stromia 

 can be distinguished (as far as I have seen) from all the 

 other species. The shell is white or dirty yellowish-brown. 

 The scutum has the lower articular ridge on its tergal 

 margin very narrow (but somewhat variable in width), ap- 

 pearing like a mere slight shoulder, against which the lon- 

 gitudinal axial ridge of the tergum abuts : it is not half as 

 wide as the short, upper articular ridge. On the under 

 side there is a very slight depression for the adductor scu- 

 torum muscle. There is considerable variation in the degree 

 to which the transverse ledge on the under side of the fixed 

 tergum projects, and therefore in the depth of the hollow 

 thus formed. The specimens with the right-side, and those 

 with the left-side opercular valves moveable, are apparently 

 about equally numerous. 



The specimen in the British Museum, from the Red Sea, 

 was attached to a Gorgonia, and was in the same box with a 

 Pyrgoma — circumstances favouring the correctness of the 



