SPIRULA. 205 



to be so, then the Spirula will assume a new importance to us 

 as the last vestige of a numerous group, else extinct. 



Three species have been described, which are thus differenti- 

 ated b} r Gray : 



Posterior part of the body holding the shell by the lateral mantle 

 flaps only, so that its last whorls are exposed below as well as 

 dorsally and ventrally. S. PERONII, Lam. 



Posterior part of the body furnished with a circular disk below, cov- 

 ering and concealing the shell, and having semicircular fin-like 

 appendages on each side. S. L^BVIS, Gray. 



Posterior part of the body as in 8. Icems ; mantle pitted with close 

 set angular depressions, giving it a well-marked, reticulated 

 character. S. VULGARIS, Leach. 



It was first conjectured by Owen* that the difference between 

 S- Peronii and S. Isems might be sexual ; but it is now plain that 

 in the animal of S. Peronii examined, the disk had been torn 

 oft', an accident which might readily occur when we consider the 

 tenacity with which the suckers adhere to foreign objects. It is 

 questionable whether the " reticulations of the mantle " in &. 

 oulgaris are specific ; they may result from a state of irritation, 

 as in the octopods. I am not disposed to place much dependence 

 on these differences. The shells seem to be indistinguishable, 

 and it will be safest to give them the name of S. Peronii for the 

 present. 



S. PERONII. Lain. PL ( .Mi. figs. 4t>7-4(>9 ; pi. 105, tig. 585. 



Animal as described in the family characters (p. 103). Shell 

 nacreous, cylindrical, conical, tapering, involute on the same 

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

 concave outwards, \vitli a shelly, ventrally placed funnel-shaped 

 siphonal tube attached to each ; last chamber rather the largest ; 

 the nuclear chamber roundish, swollen. Usual diameter, 20-22 



mill. 



Tropical Atlantic and Pacific Oceans. 



Shells are d rifled occasionally upon the Atlantic shores of the 

 United States as far north as New England, Mediterranean, 

 (Jre:it Britain. Very common in the Caribbean Sea and on the 

 shores of Australia, Xew Zealand. Cape of Good Hope, etc. 



* Zool. Voy. Samarang. 



