OCTOPODA 



383 



the funnel in the median line, forming two openings into the 

 branchial cavity ; arms with one row of suckers ; uml)rella 

 extending more than two-thirds up the arms. — South Pacific 

 (Fig. 242). 



The two pocket-like openings into 

 the branchial cavity are unique among 

 Cephalopoda (Hoyle). 



Fam. 3. Argonautidae. — Female 

 furnished with a symmetrical, unilo- 

 cular shell, spiral in one plane, secreted 

 by thin terminal expansions (the vcla^ 

 of the two dorsal arms, no attach- 

 ment muscle ; suckers in two rows, 

 pedunculate ; male very small, without 

 veligerous arms or shell. — All warm 

 seas (Fig. 243). Pliocene- . 



Fig. 242. — Amphitretus pela- 

 fjicus Hoyle, oflF Kerniadec 

 Is.: e, eyes ; /, fuuuel ; p, 

 right mantle - i^ocket. (After 

 Hoyle.) 



The shell consists of three layers, 

 the two external being prismatic, the 

 middle fibrous. Its secretion by the 

 arms and not by the mantle edge is 

 unique, and shows that it is not homologous with the ordinary 

 molluscan shell. 



The great controversy on the Argonauta, which once raged 

 with so much fierceness, is now matter of ancient history. It 



Fig. 243. — Argonauta argo 

 L., the position assumed 

 by a specimen kept in 

 captivity, the arrow show- 

 ing the direction of move- 

 ment : /, funnel ; m, mouth, 

 with jaws projecting ; sh, 

 shell, with arms as seen 

 through it ; icu, webbed 

 arm clasping shell. (After 

 Lacaze-Duthiers. ) 



--Sli^fflljjjl^ 



sh 



seems scarcely credible that between fifty and sixty years ago, 

 two of the leading zoologists of the day, Mr. Gray and M. de 



