436 BALANIDiE. 



maxillae are small ; there is a small notch beneath the two upper great 

 spines, and a second notch near the inferior angle. Between the outer 

 maxillae, there is a square-topped mentum. Hence we see that the 

 mouth in all its few peculiarities, resembles that of Coronula. 



Cirri. — These are short, with short and broad segments protu- 

 berant in front. The pedicel of the first cirrus is very broad, and 

 exteriorly clothed with fine hairs : its rami are slightly unequal in 

 length. The second and third cirri are very short. The three posterior 

 pairs are remarkable from the pairs of main spines being placed so 

 close one under the other, and in an oblique direction, that at first 

 they appear to form a single crowded transverse row : the dorsal tufts 

 are rather large. 



Body. — The body is remarkable from its nearly vertical position, 

 and from the much elongated pyramidal form of the prosoma, extend- 

 ing down nearly to the bottom of the sack. The membrane investing 

 the prosoma, presents a few circular folds, falsely appearing like arti- 

 culations. The oesophagus enters the stomach rather obliquely. With 

 respect to the generative system, I have only to remark, that the 

 vesiculae seminales are of great length, and convoluted to a remarkable 

 degree. The ovarian caeca, form a thick layer at the bottom of the 

 sack ; they do not appear to extend up the shell round the sack. The 

 only other point, which I shall here mention, is that beneath the basal 

 articulation of the first cirrus, there is a longitudinal swelling, ending 

 in a freely projecting point, '06 of an inch in length; at first, I thought, 

 that we here had a rudiment of a filamentary appendage like those found 

 in several Lepadidae ; but closer examination showed an orifice at the 

 apex, leading into the acoustic meatus, in which the singular, wrinkled, 

 heart-shaped acoustic vesicle, mentioned in the Introduction, hangs 

 suspended. Alongside the freely depending point, with an orifice at its 

 end, there is a smaller upward projecting point, without any orifice, 

 but hollow within and lined by corium ; I believe it opens internally 

 into the acoustic meatus. 



Attachment and general Growth of Shell. — All the specimens which 

 I have seen have been attached in groups. They are buried up to the 

 level of the operculum in the whale's skin; and their summits, I 

 suspect, lie even beneath the general surface of the body of the whale. 

 It is certain that the shells grow much at their basal ends. As 

 in the case of Coronula, the flat membranous basis does not actually 

 penetrate the skin ; but the general pressure of the whole group of 

 shells seems to push inwards the skin of the whale, and directly 

 beneath each shell the formation of new epidermis is apparently 

 checked. Between the shells, however, though close together, the 

 epidermis continues to be formed, and is pushed upwards between them, 

 in the same manner as it is forced into the flattened cavities on the 

 under side of the shell of Coronula. 



The manner in which a full-grown shell assumes its ordinary shape, 

 at first appears very perplexing :* it has to change from a cylinder, at 



* I am indebted to Dr. J. E. Gray for calling my attention to this subject, 

 aud explaining to me several points. 



