400 BALANID^E. 



and (/') one of the cavities between the folded walls, open 

 at the bottom of the shell, and occupied by the epidermis 

 of the Whale. The walls of the compartments, as here repre- 

 sented, (a being the rostrum, c c the lateral compartments, 

 d d the alae of the carino-lateral compartments,) are sepa- 

 rated from each other by the broad radii ; bnt if the section 

 had been taken low T down near the basis, the end of the folded 

 wall of one compartment would have been separated from 

 that of the adjoining compartment only by the close suture : 

 this will be understood by a glance at the entire shell, given 

 in fig. 3, PL 15. The rostrum of the same species, viewed 

 from the inside, is shown at fig. 1, PI. 1G ; here it may be 

 observed, that the basal margin (e e e") of the folded wall is 

 extremely oblique, the outer portion having extended down- 

 wards much more than the inner portion : this obliquity is 

 more clearly shown in the lateral view (fig. 2) of a lateral 

 compartment, for this figure will equally well serve for a 

 lateral view of the rostrum (fig. 1), if the ala (d) be supposed 

 to be removed. The section of the rostrum in fig. 7, (a), 

 will now be intelligible in relation to the view of the rostrum 

 given in fig. 1, if it be borne in mind that the section 

 has been taken high up, near the letters a, b, c" in 

 fio- 1 



As above stated, the folds or ridges in the young 

 shell become more and more transversely drawn out at 

 their ends into the transverse loops, till the latter join 

 and touch each other. In C. balanaris the lines of junction 

 are simple, though very close ; in the other species, the 

 ends of the transverse loops, where touching, are finely and 

 elegantly toothed, and thus locked together. These teeth 

 appear single when the shell is viewed either externally or 

 internally, but when the walls along the lines of junction 

 are forced apart, they are seen really to consist of transverse 

 rows of minute teeth. These teeth are less distinct, 

 forming only sinuous ridges in C. barbara (fig. 6, PL 15) ; in 

 all cases the teeth are formed by the modification of the 

 very minute beads, which ornament the lines of growth 

 on the external surface of the shell In the rostrum of 

 C. diadema t as seen internally (fig. 1, PL 10), the serrated and 

 closely-fitting lines of junction (/) between the ends of the 



