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 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, 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 

 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. 242. — Amphitretus pela- 

 giciis Hoyle, off Kermadec 

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

 right mantle-pocket. (After 

 Hoyle.) 



sh 



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; wa, 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 



