GENUS CORONULA. 413 



surrounding parts of the whale's body, these same layers 

 have been removed by disintegration. To return to the 

 section, — the outline of the boss of orange-coloured fibrous 

 tissue, under the central hollow, clearly shows that it must 

 have been formed by its own upward growth, for it 

 stands above the general surrounding level of the cor- 

 responding layer. This same conclusion is still more obvious 

 with respect to the eighteen flattened prominent horns, 

 formed of the dark epidermis ; the manner in which 

 the epidermis has been forced, moulded, and packed into 

 the eighteen flattened and curved cavities of the shell, so as 

 to adhere to them with considerable tenacity, is extremely 

 curious. The prominence of these horns is so great that it 

 appears to me quite impossible to account for them, ex- 

 cepting by a special formation of epidermis beneath each 

 cavity. The basal membrane of the Coronula, which lies 

 at the bottom of the central hollow, adheres by its own 

 cementing apparatus ; and when the larva first attaches 

 itself, this adhesion must be very important, as it allows 

 the basal edges of the shell, during their slow downward 

 growth, to press firmly on the whale's skin, and so slowly 

 indent it with the circular furrow. The final cause, pro- 

 bably, of the cavities on the under side of the shell in this 

 genus, formed by the singularly convoluted parietes, is to 

 allow of the upward growth into them of the epidermis of 

 the whale, thus securing a firm attachment and allowing the 

 shell to exert a strong downward pressure, and thus effect 

 its partial imbedment, and protection from the enormous 

 force of the waves to which it must be exposed. 



With respect to C. balanaris, I have seen only speci- 

 mens, preserved on shrunk and twisted whale's skin, with 

 the underlying fibrous layer not preserved ; but the cavities 

 in the shell were filled by horns of epidermis, exactly as in 

 C. diadema. There is, however, this difference in the at- 

 tachment of the two species, that in C. baltenaris, owing to 

 its depressed form, the circumference of the shell indents 

 the whale's skin, not vertically downwards, as in C. diadema, 

 but very obliquely outwards ; and, consequently, buries 

 itself much more completely, but less deeply, under a folded 

 and apparently ruptured flap of the epidermis. In young 



