THE SESSILE BARNACLES. 37 



F. xanthia differs from F. floridana by the color, the obtuse basal 

 edges of the wall, which is vertical on the ends and overhangs on the 

 tergoscutal side. It has some resemblance to F. entobapta, but 

 differs from that by having some short, arcuate riblets on the scutal 

 edge of the rostrum above the first rib which articulates with the 

 carina. The number of articular ribs of the movable plates and the 

 color also differ in the two species. 



One specimen somewhat smaller than the type was found in the 

 dry material from Albatross stations 2662, 2663, 2669, 2671, 2672, 

 all in the neighborhood of the type-locality. It agrees with the 

 type in the projecting adductor ridge or myophore in the fixed 

 scutum, etc. 



The type-specimen has a circular depression on the movable scu- 

 tum, probably made by a rapacious gastropod, being similar to the 

 unfinished borings often seen on bivalve nioUusks. I have seen holes 

 of tliis kind in several Verrucas. 



A variety or race of this species, which may be called Verruca 

 xanthia insculpta (pi. 6, fig. 2), is represented by one individual, Cat. 

 No. 32925, U.S.N.M., taken at Albatross station 2415 or 2416 (the 

 material from these two stations was not separated), both being very 

 close to the type-locality of F. xanthia. It has more pronounced 

 sculpture than the type; the movable scutum being radially ribbed 

 throughout, five ribs extending to its basal margin. The fixed 

 scutum and tergum have strong, well-spaced growth-lines parallel to 

 the basal margin. The fixed scutum has a deep adductor pit within, 

 situated in the upper half of the plate, but the lower margin of the 

 pit does not project as a myophore. The fixed scutum occupies a 

 smaller segment of the wall, and the rostrum a larger. The suture 

 between movable scutum and tergum inside is almost straight, except 

 near the apex. 



Carinorostral length at base, 5 mm. ; carinorostral length between 

 beaks, 6.5 mm.; diameter at right angles to preceding, 6 mm.; height 

 of fixed tergum, 3.5 mm.. 



This barnacle agrees with the less spreading forms of F. floridana 

 in general shape and pattern of sculpture, but it differs by the steeper 

 walls with obtuse basal edges, the more numerous teeth of the carino- 

 rostral suture, the stronger sculpture, the absence of a projecting 

 myophore within the fixed scutum, and the color of the plates, outside 

 and within. 



It was seated with the carinorostral axis obliquely transverse to 

 the supporting branch of white coral. 



Another specimen has a quite shallow adductor pit in the fixed 

 scutum. The suture between movable scutum and tergum, inside, 

 is bisinuate as in typical F. xanthia. The rostrum is very large. 

 Carinorostral length between apices 8 mm. 

 4729 Bull. 9316 4 



