XIII 



OCTOPODA 



383 



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

 branchial cavity ; arms with one row of suckers ; umbrella 

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

 (Fig. 242). 



The two pocket-like openings into 

 the branchial cavity are unique among 

 Cephalopoda (Hoyle). 



Fam. 3. Argonaictidae. — Female 

 furnished with a symmetrical, unilocu- 

 lar shell, spiral in one plane, secreted 

 by thin terminal expansions (the vela) 

 of the two dorsal arms, no attachment 

 muscle ; suckers in two rows, pedun- 

 culate ; male very small, without 

 veligerous arms or shell. — All warm 



seas (Fig. 243). Pliocene . 



The shell consists of three layers, 



the two external being prismatic, the ^'%c!t^'Hoy?J!^orKTrnfadec 

 middle fibrous. Its secretion by the is.: e, eyes; /, funnel; p, 



arms and not by the mantle edge HoyieT^^^ ^"^^^ ^ ^^ 



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; loa, webbed 

 arm clasping shell. (After 

 Lacaze-Duthiers.) 



seems scarcely credible that between fifty and sixty years ago, 

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



