during their Growth and Development. 11 



value lias generally been accorded; 2, by the complete absence 

 of scales outside the corselet, whilst in the Orcyni of the same 

 size the skin is already clothed with small scales, the conse- 

 quence of which is that the limits of the " corselet " in the 

 adult tunny and albacore are somewhat obscure, so that, 

 properly speaking, we cannot say there is a distinct corselet 

 in those species ; 3, by an important osteological character, 

 jiamely the special development, in the form of a net or trellis, 

 of a portion of the abdominal part of the vertebral column 

 between the vertebrae properly so called and the lia^m apo- 

 physes, a development which has already been described by 

 Cuvier. This organization is common to T. thunnina and 

 T. pelumysy and occurs in a modified form in Auxis, while 

 in this respect Orcynus gernio presents essentially the same 

 character as 0. thynnus and the species belonging to the 

 genera Cybium and Pelamys. Whether this is or is not the 

 case in Urcynopsis [unicolor) is unknown ; but there is reason 

 to suppose that it presents some of the characters belonging to 

 Auxis and to Thynnus (m.). 



Pelamys chilensis and P. orientalts are certainly not dif- 

 ferent species, any more than Thyr sites chilensis and T. atun. 

 It is by error also that a corselet of scales has been denied to 

 the genus Cybium ; this is already distinct in very young 

 individuals, and extends, in the usual way, round the base of 

 the pectorals and ventrals, along the dorsals, &c. j but, it is 

 true, it is less apparent than in the other Thynnoids. The 

 species included in the genus Cybium differ in general by 

 rather insignificant characters, which, however, seem to be 

 more constant than might have been expected. There is 

 therefore no reason for reducing them in the same proportion 

 as the species of the Thynnus- Orcynus group; moreover it 

 would appear that they are far from being so pelagic as the 

 species belonging to the latter group. Among the species of 

 Cybium proper inhabiting the Atlantic, I have been able to 

 distinguish without difliculty C. caballa (of which C. imma- 

 culatum is no doubt the young form), C. regale ^ and C. inacu- 

 latum ; C. acervum is a young C. regale^ and has nothing to 

 do with C. caballa. 



There is, however, a species of Cybium which must be 

 generically separated from the rest, namely the large truly 

 pelagic and rather rare Thynnoid, attaining a length of more 

 than seven feet, which our sailors call the " barracotta," and 

 of which they have sometimes brought us the head and caudal 

 fin ; it is met with in the Atlantic north and south of the 

 equator, in the Mediterranean, and in the Pacific Ocean, but 

 much more rarely than the bonitos and albacores. It is the 



