CEPHALOPODA. — BERRY. 289 



Remarks. — Opisthoteuthis is not, even after all the years 

 since its original description, so common a genus but that the 

 discovery of specimens is almost per se a matter of consider- 

 able interest. Their comparative abundance in the present 

 instance is therefore rendered especially noteworthy. These 

 Australian examples differ from the type of the genus and 

 approach the Japanese 0. depressa in the very great extent 

 to which the compression of the body has been carried. 

 O. agassizii further differs in that its pteropallial cartilage is 

 a paired organ, its components being said to extend into the 

 fins on either side. This featvire would certainly seem 

 important enough for taxonomic recognition, and is the 

 principal basis for the establishment of the subgenus here 

 proposed. 0. depressa also falls under Teuthidiscus rather 

 than the typical group, and I suspect that both the other 

 described species, 0. medusoides, Thiele and 0. extensa, Thiele, 

 belong here likewise, though their skeletal characters have 

 not yet been made known. Superficially at least, 0. extensa 

 seems nearer to the form now describecl than do any of the 

 other species, so much in fact that it is not impossible that 

 it may prove conspecific when better known. However, from 

 Thiele's description and figures it would appear to have 

 smaller, more median fins, a less extensive umbrella, more 

 attenuate arms, and smaller, more uniform suckers. It is 

 not represented as areolate. The gills are said to have only 

 six divisions, as against eight in 0. pluto. But it must be 

 said that none of these dift'erences are very striking. 



Even small specimens of O. pluto, down at least to a 

 diameter of 75 mm., are readily distinguishable by their 

 characteristic coloration, as well as usually by their usually 

 flabbier, stringier, and less gelatinous consistency than that 

 shown by {e.g.) specimens of 0. persephone. The depressed, 

 discoid outline, however, does not invariably hold in preserved 

 material. In several specimens, notably E4321, the body is 

 elevated and slightly constricted at the junction with the 

 umbrella, while in a few specimens, as E4319 and E4320, the 

 umbrella is closed and the body pushed out so that the general 

 shape more approaches that of a Cirroteuthis. 



Portions of skin containing areolae were delaminated and 

 mounted. Both stained (Delafield's hsematoxylin) and un- 

 stained preparations were made in the hope of obtaining 

 some clvie as to their nature or the possibility of the nuclear 

 mass containing photogenic tissue. But the tissues proved 

 to have suffered too much disorganisation to show their true 

 character or to justify further investigation by sectioning. 

 The central clear region was conspicuous as a circular or 



