CAETIL \ 



cartilage it< two narrow posterior blade-like projections (d, same 

 Sg.). -In the genus Cirroteuthis, an .-mom-Jons o.-topod ,,r which 

 only a sin-le species is known, the dor-d cartilage is very broad, 

 so as te simulate the internal shell or pen of the decapod. Ai 

 the entrance of the anterior ventral mantle opening is rnn>l :) 

 sin-ular cartilaginous mechanism, which ,p( ),-|,j,,- nv |,o s ( ..,]] r( j 

 ""' "appareil de resistance," peculiar bo tin- cephalopoda, whirl, 

 consists of buttons or ridges and corresponding grooves placed 

 on the opposed inner side of the mantle ami the body, and h v 



which the animal may at will button its head to the mantle to 

 prevent the injury which might otherwise result to it duril 



struggle with wave or prey, in consequence of its want of support 

 there (Plate 1. li-. 2). QII the other hand, by relaxing this sup- 

 port the animal preserves Tor itself a freedom of movement of 

 \^<\ ami arms which would he impracticable were these as per- 

 manently and closely connected with the body on the ventral as 



they are on the dorsal side. The arrangement of this resisting 

 ;PP-'"-'t"s Caries in different genera, and is : , ^nl distinctive 



character. Lar-ely developed in those species which have no 

 i attachment to the body. MS i n Oinmastrepl.es, Loli<,- , ,.,,-.. 

 it exists ; ds> in those genera which possess only a very small 

 cervical band of attachment, as in Argonauta, bul it is wanting 

 in those genera in which the permanent banfls are Well-developed, 

 as in Octopus. (Vnndiia. etc. 



In PhUonexiS Or Tremoctopus, a button is found at the base 

 of the siphon tube, with a corresponding groove to receive il 

 upon the inner wall of the mantle, but in Argonauta the relative 

 position of button and buttonhole is reversed. In Kossia we find 

 a short ridge surmounted by a profound groove opposed to an 



elongated groove on the base of the siphon ; in Loli-o and Sepi- 

 ot'-uthis (li-. -2) the i-id-e is somewhat longer, without grooves ; 

 in Onych-.tciithis and Km.ploteut his the ridgv is nearly hall' the 

 length Of the body, with ti,e siphona! groove; in Sepia an obli,p,e 

 oblon- button can be fixed into a similarly formed pit upon the 

 siphon: in CMroteuthis there are an obi,,,,- Ion-it udinal button 

 and two lat,-ral pits fittin- int., a central pit and two buttons on 



lll(1 siphon; liually. in Ommastrephes, in which it is mosl com- 



plicated, there are two projections. , ol,|,, n - M nl the other 



triangular, entering cavities upon the siphonal tube, an, I two 



