464 balaniujE. 



hollow or are pitted : the radii, in fact, may be said to be folded, like 

 the parietes, only more symmetrically and narrowly, so that the points 

 in the opposed edges interlock. The edges of alae are serrated, but 

 more finely than the radii. The parietes are rather thin, with their 

 under surfaces generally smooth. The sheath does not descend far 

 down the shell. The colour of the corium lining the sack and the 

 animal's body varies considerably, being either almost black or pale 

 purple; and the specimens adhering to ships' bottoms are internally 

 almost white. Of these latter specimens, I have seen some *6 of an 

 inch in basal diameter : of corroded specimens attached to littoral 

 shells, I have not seen one quite '4 of an inch in basal diameter. 



Scuta, with the articular ridge very prominent : the pit for the 

 adductor is deep, and there are generally some distinct, though 

 minute, pits for the lateral depressores. The Terga (fig. 3 c) have the 

 articular ridge very prominent ; and the carinal margin is rather more 

 arched and protuberant than in the other species. 



Mouth. — The crest of the labrum is toothed: the palpi are short, 

 truncated, with long spines arising from their ends, and along the 

 basal exterior margin. In the mandibles the first tooth is seated rather 

 far from the succeeding teeth: the inferior part is coarsely pectinated: 

 the maxillae are deeply notched. The tips of second pair of Cirri have 

 many coarsely pectinated spines : the shorter ramus had six segments, 

 whilst the shorter ramus of the third pair had eighteen segments : the 

 segments on the posterior cirri carry five pairs of main spines. 



Branchiae, fyc. — These consist of a double fold, the outer one being the 

 largest, and the inner semi-circular, as has been described under the 

 genus. In a young specimen, only one tenth of an inch in basal diameter, 

 the branchiae consisted of a single fold ; in a specimen a little larger, 

 there were two folds, but these were of equal size': ultimately the outer 

 fold increases in size so as to become nearly double the inner fold. 

 The Ovarian tubes are remarkable from their large diameter. I was 

 surprised to observe in the specimen only one tenth of an inch in basal 

 diameter, that the larvae were ready to escape. On the prosoma, there 

 are some longish hairs arranged in short rows, and some few on the 

 membrane lining the sack, and some on the opercular membrane and 

 valves. 



It may be seen in PL 18, fig. 3 a, and 3 b, that I have 

 here united two varieties considerably different in external 

 aspect : I have done this without hesitation, inasmuch as 

 there are intermediate forms, and as the differences are 

 analogous with those so commonly occurring in sessile cirri- 

 pedes, dependent on whether or not the specimens have 

 been exposed to corrosion. I have seen both varieties from 

 Natal, and both from the west coast of Africa; although the 

 smooth, well-preserved, narrowly plicated varieties seem 

 more common in western than in southern Africa. With 

 respect to the range of the species, I have seen a specimen 



