180 OMMASTREPHES. 



O. SLOANII, Gray. 



Body cylindrical, rather tapering behind ; fins rhombic, rather 

 more than one-third the length of the body ; arms compressed, 

 the third pair acutely finned, with a narrow rayed membrane on 

 the inner edge of the ventral side; tentacles slightly keeled 

 externally, base half naked ; cups of lower part small, in two 

 rows, of middle in four rows, the seventh pair of the central 

 series largest (rings with distant teeth all round), of the apical 



part in three or four rows. 



New Zealand ; Indian 0. 



Described from specimens in Mus. Brit., and not figured. The 

 description does not indicate any great difference from the two 

 preceding species. 



f f f Second and third pairs of arms with a broad, metnbranaceous fin or 



wing onthe inner edge of the ventral side, supported by radiating fleshy 



rays arising front, the base of the cups. Cups in two distinct 



rows; ventral part of the mantle free from the head. 



O. BARTRAMII, Lesneur. PL 80. figs. 3i;l. 8i;-2. 



Body elongate, cylindrical, acuminate posteriorly ; fins dilated. 

 rhomboidal, the angles acute; head short: arms short, biangu- 

 lated or triangulated dorsally ; tentacles large, short, biangulated. 

 Shell very narrow, the extremity enlarged. 



Total length, 10 inches, length of body. 15 inches. 



The chromatophores are aggregated into a dark dorsal band. 

 West Indies ; Gulf Stream ; Gape of Good Hope f 



f t t f Second and third pairs of arms with a broad membranaceous fin on 



the inner edge of the ventral side, supported by radiating fleshy rays ; 



cups compressed so as to be generally in a single series. 



O. OUALANIENSIS, LeSSOIl. PI. S 1 . II g. ol'>8. 



Body elongated, cylindrical; fins terminal, broad, transverse; 

 arms short, unequal, furnished with one row of cups, tentacles 

 much longer than the arms. Shell elongate, narrow. 



Total length about (i inches. 



Indian Ocean ; Gape of Good Hope ; Pacific Ocean. 



O. THYONII. (Jabb. PI. s|. figs. :rr2. :J7o. 



Body elongated, cylindrical, tapering t<> a point behind; (ins 

 transversely rhomboidal. between one-third and one-fourth the 

 length of the body ; arms short, compressed, robust, compara- 



