516 SPIRULID^. 



Family SPIRULID^. 



Eyes covered with the skin, with a lower eyelid. Buccal mem- 

 brane without cups. Sessile arms triangular, tapering. Cups nu- 

 merous, equidistant, very small, slightly pedicelled, in six longitu- 

 dinal series. Tentacular arms elongate, peduncled, cylindrical ; 

 club — ? Siphuncle conical, with an apical valve. 



Body sub-cylhidrical, oblong, end rounded, sometimes furnished 

 with a thickened belt, and with a small fleshy semi-lunate fin on 

 each side. Mantle free all around ; cartilage, on the inner side of 

 the ventral surface, linear. 



Shell internal, shelly, spiral, chambered ; chambers furnished with 

 a siphon ; the last chamber large enough to contain but a very small 

 part of the animal. 



In the only recent genus, Spirula, the apex of the shell is simply 

 hooked ; in the fossil genera it is enveloped in a thickened lamhial 

 coat produced behind, as in Spiralirostra. 



Oenus SPIRUL.A, Lamarck. 1799. 



Fins two, small, caudal, on the side of the extremity of the back. 

 Eyes large. Cups of sessile arms in six longitudinal rows ; rings 

 entire, or very minute, and denticulated ; third and fourth arms 

 shortly webbed, the rest free. Siphuncle with an apical valve. 



Shell calcareous, cylindrical, conical, tapering, involute on the 

 same plane, the whorls separate from each other and chambered ; 

 septa concave outwards, with a shelly funnel-shaped siphon on the 

 inner or most curved side, traversing each cell without communi- 

 cating with each other. 



Spirula fragilis. 



Nautilus spirilla, Lin. ; Blainv. Mai. pi. 4, fig. 1 ; Encyc. Moth. 465, fig. 5. 

 Spirilla frarjil is, Stimpson, Check Lists, 6 (1860). 



Spirula Peronii, Lam. An. sans Vert. — Gould, Inv. 317 (1841). — De Kay, N. Y. 

 Moll. 5, pi. 3.5, fig. 8 (1843). 



This is the only species of the genus known. It inhabits the open 

 sea, and is sometimes found, after storms, upon the shores of Nan- 



