THE SESSILE BARNACLES. 27 



(1) The Blake took four specimens in 195 fathoms off Florida, on 

 a spine of Dorotidaris abyssicola A. Agassiz. The base of one of 

 these is drawn in plate 2, figure 2. They are much larger and 

 especially longer than the typical form of V. alba. The rostrum 

 extends entirely around the rostral end and its wall slopes outward 

 toward the base. The basal edge is very obtuse, flat, but not inflexed. 

 The rostrum and carina each have 5 articulating teeth and ribs in 

 the largest, but in smaller ones there are four. The right scutum 

 and tergum are movable. In one example a minute rib has split 

 off from the second articular rib of the tergum, a corresponding one 

 appearing also in the scutum. The largest specimen measures: 

 greatest carinorostral length 7 mm., length between apices 5 mm., 

 height 2.5 mm. 



The terminal appendages are 2.5 mm. long, of 28 segments (pi. 9, 

 fig. 2). The penis is nearly 3 mm. long, being nearly three tunes the 

 length of the protopod, and about three-fourths that of cirrus vi. 



The cirri and mouth-parts are substantially as described for typical 

 V. alba. 



(2) The lot taken by Mr. Henderson in the Eolis, on the Pourtales 

 Plateau near Key West (pi. 2, figs. 1-1&), contains numerous examples 

 of all ages, all of them sitting upon Dorocidaris spines, and all agreeing 

 in having thinner walls than other colonies seen. The shape is long, 

 as in the Blake specimens, the rostrum being produced around the 

 end and outward farther than in the typical V. alba. The basal 

 edges are thin in about a dozen individuals of various sizes removed 

 from the spines. 



The movable scutum is arched or convex, being depressed and 

 somewhat twisted toward the acute apex. Articular ribs three, 

 counting that terrninatiag at the basotergal angle, the rest of the 

 surface transversely grooved and longitudinally bicostate. Internally 

 it is excavated toward the apex. 



The movable tergum has four articular ribs, the second one slightly 

 smaller or very small. The rest of the plate is transversely grooved, 

 often with some short longitudinal ribs. 



The fixed scutum and tergum have recurved, produced apices, 

 rather near together. Parietal surfaces irregularly roughened, sim- 

 ilar to those of the rostrum and carina. There is a hollow for the 

 adductor muscle, with a narrow adductor ridge below, in the fixed 

 scutum. The rostrum and carina interlock in a zigzag suture pro- 

 duced by about four teeth in each plate, the upper two teeth large hi 

 each. The beaks of the plates bend over toward the movable plates, 

 especially that of the rostrum. The scutotergal borders of both 

 rostrum and carina have short, arcuate riblets terminating on the 

 scutal and tergal borders. A large individual measures: Carino- 

 rostral length of base 5 mm., between apices 3.8 mm., breadth of 

 base 2.2 mm., greatest height 2.8 mm. 



