44 SriRULIDiE. 



Fam. SPIRULID^. 



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

 membrane without cups. Sessile arms triangular, tapering. 

 Cups numerous, equidistant, very small, slightly pedicelled, 

 in six longitudinal series. Tentacular arms elongate, 

 peduncled, cylindrical ; club — ?. Siplmncle conical, with 

 an apical valve. 



Body subcylindrical, oblong, end rounded, sometimes 

 furnished with a thickened belt, and with a small fleshy 

 semilunate fin on each side. Mantle free all round ; car- 

 tilage, on the inner side of the ventral surface, linear. 



Shell internal, shelly, spiral, chambered ; chambers fur- 

 nished with a siphon ; the last chamber large enough to 

 contain but a very small part of the animal. 



In the only recent genus, Splrula, the apex of the shell 

 is simply hooked; in the fossir genera it is enveloped in a 

 thickened laminal coat produced behind, as in S_piriiltrostra. 



Genus SPIRULA, Lamarck. 



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

 the back. Eyes large. Cups of sessile arms in six longi- 

 tudinal rows ; rings entire, or very minute, and denticu- 

 lated ; 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, tra- 

 versing each cell without communicating with each other. 



Ex. S. Inevis, Gra?/, pi. 5, fig. 3. Shell, S. prototy- 

 pus, Peron, fig. 3, a. 



