POLYPODA. 45 



The shell is placed vertically in the posterior part of the 

 body, with the involute spire towards the ventral side. 

 The last chamber is not larger in proportion than the rest ; 

 its margin is organically connected ; it contains the ink- 

 bag (Woodward). In its habits, Spirula is, probably, 

 pelagic, swimming near the surface in calm weather, prey- 

 ing on small acalephte towards the evening, and sinking 

 below the surface during the day. Although the shell has 

 been long well known, and is found scattered by thousands 

 on the shores of New Zealand, only one perfect specimen 

 has been met with, brought home from New Zealand 

 by Mr. Earl, and figured by Mrs. Gray, in the " Annals 

 and Magazine of Natural History." M. De Blainville de- 

 scribed an imperfect specimen sent home by M. Peron ; 

 Mr. Crouch procured a fragment ; and an injured speci- 

 men was obtained during the voyage of H.M.S. " Sa- 

 marang,"" and served Professor Owen for an elaborate 

 memoir of its anatomy. 



Species of Spirula. 

 prototypus, Feron. 



Sub-gen. lituus, Brown. 



Posterior part of the body furnished with a circular disc 

 covering and concealing the shell, and with semicircular fin-like 

 appendages on each side. 



Isevis, Gray. reticulata, Owen. 



Order POLYPODA. 



Body without fins, enclosed in the last chamber of a 

 siphon -chambered external shell. Head not separate 



