THE SESSILE BARNACLES. 35 



This form varies in the pose of the movable plates, which vary 

 from a subvertical to a subhorizontal position in different examples. 

 The sculptm'e of the movable scutum is somewhat more elaborate 

 than in the type of V. calotheca, having three (or, in one individual, 

 four) longitudinal ribs on the Oiccludent area. The color differs, 

 especially inside. The movable plates slope more steeply. The 

 interlocking teeth of the carina and rostrum are more regular and 

 the ribs ruiming to them are stronger. In V. calotheca the upper 

 ribs and teeth are decidedly larger than the lower oues. There are 

 also slight differences in the scutotergal sutures, both in the movable 

 and fixed plates. Three specimens were taken at the type-locality; 

 one at Station 2666. All were seated upon coral lirauches. 



VERRUCA CALOTHECA HETEROPOMA, new subspecies. 



Plate 5, figs. 1, la. 



Type.— Cat. No. 32932, U.S.N.M. 



Ti/pe-localitij. — Albatross station 2753, near St. Vincent, West 

 Indies, north latitude 13° 34'; west longitude 61° 03', in 281 fathoms, 

 bottom temperature 48° F., on slender, branching coral, and on an 

 echinoid spine. Also Blalce collection, oft" St. Vincent, in 88 fathoms, 

 on spines of Cidaris ajjinis Philippi. (Museum of Comparative 

 Zoology.) 



Tliis barnacle, known by eight individuals from the type station, 

 and two from an adjacent BUike station, resembles V. calotheca inter- 

 nally and in most details of external form. It differs by the sculpture 

 of the movable plates. The movable scutum has two broad articular 

 ribs (in F. calotheca and V. c.jiavidula there are four articular ribs), 

 and a much naiTOwer, though more prominent, third crescentic rib 

 terminating at the basitergal angle. There is also a minute rib 

 under the apex, foniiing the upper border of the tergal edge, as 

 usual. 



The movable tergmn has three articular ribs, including the diagonal 

 rib (whereas in V. calotlieca and V. c. flavidula theve are four). The 

 apex of the rostrum projects. Carinorostral sutm'al region about 

 as in V. calotheca. 



Carinorostral length between apices 5,5 mm. ; greatest diameter at 

 right angles to the length 5 mm. ; height of fixed tergum 2.6 mm. 



The rami of ciri'i i and ii are unequal, the anterior being about 

 three-fom'ths the length of the posterior ramus. The terminal 

 appendage of 14 segments is about one and one-half times the length 

 of the protopod, and one-third that of cirrus vi. The penis is 2.4 mm. 

 long, about half as long as cirrus vi. 



In one individual the median articular rib of the tergum is bifid, 

 and a minute rib split off from the second rib of the scutum articulates 



