THE BARNACLES IN THE U. S. NATIONAL MUSEUM. 107 



based, chanoe somewhat with age, and without a series of specimens 

 it is often difficult to tell whether a form in hand is 3'oung or mature. 

 The general contour is certainly affected bj^ the shape of the support- 

 ing surface; and any species may occur with the movable valves on 

 either the right or left side. Gruvel and Aurivillius have described 

 a considerable number of forms, many of them very closely related, 

 from the eastern Atlantic; so that the study of Verruca is now b}' no 

 means a light task. 



Among the species taken in the western Atlantic and Antilles by the 

 Albatross I have been able to recognize only one previously described 

 form, the Verruca nexa of Darwin, which was taken at one station off" 

 Habana. The forms described below as V. euglyjAa and V calotheca 

 belong to a group of closely related species or races, widespread in 

 deep water, yet they present minor features which bar their identifica- 

 tion with any forms hitherto described and figured. Verruca darunni 

 stands near V. nitida Hoek, from the Moluccas; V. hoehi^ on the 

 other hand, is quite distinct from other described species. 



No other forms of this family are known from North American 

 waters. 



VERRUCA NEXA Darwin. 



Locality. —C2±. No. 9496, U.S.N.M., Alhatross Station 2324, north 

 latitude 23^ 10' 25", west longitude 82° 20' 24", off Habana, Cuba, in 

 33 fathoms. 



In some of the specimens there are strong vertical ribs on the fixed 

 scutum and tergum, while in others of the same group the wall on that 

 side is nearly smooth. 



VERRUCA NEXA ALBA, new subspecies. 

 Plate XI, figs. 7, 8. 



Type.—C^t. No. 9474, U.S.N.M. 



Type-locality. — Alhatross Station 2317, Straits of Florida, north lati- 

 tude 24° 25' 45", west longitude 81° 46' 45", in 45 fathoms on a sea- 

 urchin spine. 



This form resembles V. nexa in size and general shape of the plates, 

 but the movable scutum is convex between apex and basal margin, the 

 former being depressed and somewhat twisted; the two articular ridges 

 are weaker. The rest of the plate has three strong, slightly beaded 

 radial ribs. The movable tergum has four articular ridges, the sec- 

 ond one very small. The apices of the fixed scutum and tergum are 

 produced in short, stout beaks. Both carina and rostrmn have several 

 short, curved ribs terminating on the hinge-line of the movable plates, 

 and each has one very large articular rib, ending in a long interlocking 

 tooth. The shell is white. Length 4, breadth 2.7, altitude 1.7 nun. 



Another specimen on the same spine has four strong, subequal 



