226 SCALPELLUM VULGARE, 



four times as wide as high j their internal surfaces are 

 slightly concave, and their external, convex ; the two ends 

 are pointed. Viewed internally, the scales approach in 

 shape to rhomboids. There are, in a medium-sized speci- 

 men, about twenty scales in each whorl, their tips over- 

 lapping each other : the whorls are placed not very near 

 each other and at rather unequal distances, except round 

 the uppermost part, where, being in process of formation, 

 they are packed closely together. The membrane uniting 

 the scales, supports numerous transverse rows of articu- 

 lated spines, varying from ^th to^th of an inch in length, 

 and each furnished with a long sinuous tubulus, To^th 

 of an inch in diameter, running through the membrane 

 to the underlying corium. 



Attachment. — Specimens are attached to various horny 

 corallines, and occasionally to the peduncles of each 

 other.* In both cases, supposing the coralline to be 

 erect, the capitulum is placed upwards, with its orifice 

 towards the branch to which it is attached, and conse- 

 quently with its carina outwards. Where several are 

 crowded in a group, their peduncles often become twisted 

 and their positions irregular, with their orifices facing 

 in any direction. This uniform position is simply the 

 consequence of the larva attaching itself head-downwards, 

 and from the position of the prehensile antennas, neces- 

 sarily with its sternal surface parallel and close to the 

 branch of the coralline ; hence the dorsal surface, which 

 afterwards is converted into the carina, faces outwards. 

 The peduncle, as already stated, often tapers, at its basal 

 extremity, to a sharp point. In very young specimens, 

 for instance in one with a capitulum only ^th of an inch 

 in length, the method of attachment is the same as in 

 Lepas and many other genera, namely, by cement pro- 

 ceeding exclusively from the antennae of the larva ; but 

 in older and full-grown specimens, instead of the whole 



* Mr. Peach, (Transact. Brit. Assoc, 1845, p. 65,) states that this is 

 sometimes the case in Cornwall ; and I have seen a similar instance in a fine 

 group from Naples. 



