of British Mollusca. 459 



" This species is the type of a very distinct genus, especially 

 remarkable for being the only known genus among Myopsidse 

 that has round pupils and the eyelids free all around. In 

 fact it shows quite conclusively that this division of the Deca- 

 cera into two groups, based on the presence or absence of free 

 eyelids, is purely artificial and of little or no systematic 

 value." The conclusion I arrive at is that the division of 

 the Decapoda into two primary groups by the character of 

 the eye should be regarded as of secondary importance. Thus 

 viewed the Oigopsida are a specialized and very natural 

 group which should be kept together near to Loligo, while 

 other considerations come in which appear to point to the 

 desirability of breaking up the group Myopsides, though 

 Steenstrup still maintains the Myopsides and Oigopsides as 

 primary divisions. 



The arrangement by their shells was first put forward by 

 J. E. Gray *. He divided the Decapoda — or Sephenia as he 

 called them — into three suborders, I. Chondrophora, II. Se- 

 piophora, III. Belemnophora. Dr. Paul Fischer f has, in 

 his recently published work, followed this arrangement, only 

 substituting the preferable term Phragmophora for that of 

 Belemnophora. This appears as a whole a very natural 

 arrangement, and in it we seem to find the best guide to the 

 archaic history of the class. The Phragmophora have the 

 shell divided into air-chambers, as, for example, in the recent 

 genus Sjrirula, in which " the multilocular shell corresponds 

 with the phragmocone of the Belemnite " (Owen) ; and this 

 recent genus is at once distinguished from the Sepiophora not 

 only by the character of the shell, but by the absence or very 

 rudimentary condition of the fins. Next come the Sepiophora, 

 in which the septa are exchanged for a series of continuous 

 calcareous deposits, forming an internal shell of considerable 

 size, but of such a spongeous character as still to be capable 

 of retaining air; while the animal, which bears the sepia 

 shell, differs from the Phragmophora and Chondrophora in 

 its wide depressed form and in its tins, which usually fringe the 

 whole length of the body. It agrees with both in having one 

 of the lower or ventral arms in the male sexually affected ; 

 but here the hectocotylization is usually at the base, in the 

 others at the extremity of, or rarely throughout, the arm. 

 Next Ave come to the Chondrophora, where we find that 

 " the primitive shell-gland and shell-sac have become fused " 



* Brit. Mus. Cat., Cat. Mollusca in Coll. of B, M. pt. 1, Cephalopoda 

 antepedia (1840). 



f ' Manuel de Conchvliologie et de Paleontologie conchvliologique ' 



(1887). 



