ALC1PPE LAMPAS. 531 



nearly parallel to one or the other side of the capitulnm. 

 On the carinal side, the capitulum is generally separated 

 from the peduncle by a rather deep fold (f, in the section 

 tig. 5), but this depends in some degree upon the state of 

 distension of the mass of ovarian caeca. I have given a 

 drawing, fig. 1 (partly taken from Mr. Hancock), of a very 

 regular individual, and of an extremely distorted specimen 

 (fig. 2). The distortion, I believe, is generally caused by 

 the animal, during its excavation, breaking into some old 

 cavity. 



External Structure. — The orifice leading into the sack is 

 about one third of the total length of the animal : its edges 

 or lips are thickened, horny, and brownish : at the lower end, 

 exactly where the orifice ends, the lips are formed, from 

 being deeply notched, into two sharp projections {a, figs. 

 1, 5, 6), unlike anything occurring in any other Cirripede. 

 The external membrane {c, fig. 6) of the lip supports an 

 irregular but nearly straight band of sharp, thick spines of 

 chitine, about -r^th of an inch in length, together with a 

 few hairs : at the carinal or upper end of the orifice the 

 spines are largest and most numerous; at the other and 

 lower end, they decrease in size ; and on the two projections 

 (a, fig. 6), and on the adjoining parts, of the external 

 membrane, they graduate into the small dentated points 

 which cover the whole surface of the animal. The inner 

 tunic of the sack (b), on each side along the upper half of 

 the orifice, is remarkable from having a moderately broad, 

 curved band of short, sharp spines, not quite so thick as 

 those on the external surface, closely adpressed together 

 and pointing upwards, like the javelins of an ancient phalanx, 

 thus probably preventing the ingress of any intruding animal. 

 This band of spines curves at the upper end, conformably 

 with the shape of the orifice. The inner tunic of the sack 

 in this upper part is yellowish, and, what is very unusual, is 

 thicker than the external membrane. A little way down, 

 within the orifice, and more especially in front of an elegant 

 row of hairs on the two sides of the great labrum, there is 

 a band of very fine but stiff hairs G^ths of an inch in 

 length), pointing upwards, and making together with those 

 on the labrum a hedge, barring ingress into the sack. 



