522 VKRRUCID.E. 



sometimes larger than in V. Stromia (but never so large as 

 in V. laevigata), and is placed more in the middle of the 

 tergal margin : but by far the most important character by 

 which this species can be distinguished from all the others, 

 is the presence, on the under side of the moveable scutum, 

 of a straight, prominent adductor ridge, which runs up to 

 and even under the apex of the valve, for it is there slightly 

 hollowed out. In the moveable tergum, owing to the 

 medial position of the lower articular ridge of the scutum, 

 the middle of the scutal margin is more hollowed out, and 

 the axial ridge narrower, than in V. Stromia. 



In the animal's body the only difference which I could 

 perceive was that the shorter rami of the second and third 

 pairs of cirri were not so short, compared either to the other 

 cirri or to the longer rami of these same cirri. In the 

 second cirrus, in a moderately-sized specimen, the seg- 

 ments were six and thirteen in number in the two rami, 

 and in the third cirrus, seven and fifteen. 



Had it not been for the specimen in the British Museum 

 of V. Stromia, from the Red Sea, I should have con- 

 cluded, from geographical considerations, that V. Spengleri 

 probably was the species found in the Mediterranean, and 

 noticed by Spengler (' Schriften der Bed. Gesell.,' 1 B., 

 1780), as a small variety of the northern V. Stromia; and 

 likewise that it was the Creusia echinoides of Risso (' Hist. 

 Nat. Product, de l'Europe/ torn. 4, p. 382, 1826), which 

 is certainly a Verruca, but not described with sufficient 

 minuteness to be recognised. 



4. Verruca nexa. PL 21, fig. 5. 



Shell reddish : moveable scutum, with three strongly pro- 

 minent longitudinal ridges, besides the articular ridges : 

 fixed scutum larger than the carina, with no distinct adductor 

 plate. 



Hub. — West Indies, Mus. Brit. ; attached to a Gorgonia. 



This species differs considerably from all the others in 

 the genus. The shell is brownish-red, tinted yellow : it is 



