GASTEROPODA. 53 



AKERA. 



Oval-oblong, thin, flexible ; spire short, truncate, whorls distinct. 



* 247. A. tumida, Adams. Shell sub-cylindrical, rather straight, 

 with a single central band of brown ; spire contracted, flat, with the 

 last whorl tumid above ; aperture rather square in front, contracted 

 behind, with the outer lip a little produced above the centre ; columella 

 rather straight, narrow. (Reeve.) 



FAMILY PHILINIDJE. 

 Shell internal, or none ; bulla form, but slightly convoluted. 



PHILINE. 



Shell fragile, ovate, convolute, spire none, aperture very large, open. 



248. P. angasi, Crosset?'), Journ. de Condi., 1865, pi. 2, f. 5. 

 Shell white, slightly iridescent. 



Allied to P. quadripartita, Adams. 



FAMILY APLYSIID./E . 



Shell none or rudimentary and covered by the mantle, oblong, 

 trigonal or slightly convoluted. Animal slug-like; foot drawn out 

 into a tail behind ; sides with extensive lobes reflected over the back 

 and shell. 



APLYSIA. 



Shell semicircular, membraneous or sub-cartilaginous ; head with 

 four tentacles. 



249. A., sp. ind. Shell pellucid, whitish, very finely radiately 

 striate. 



A single shell from the Bay of Islands. 



O RDER NlTDIBR ANCH IATA. 



Animal destitute of a shell, except in the embryo state ; branchiae 

 always external, on the back or sides of the body. 



FAMILY DORIDJE. 



Animal oblong ; gills plume-like, placed in a circle on the middle 

 of the back ; tentacles two ; skin strengthened with spicula, more or 

 less definitely arranged. 



DORIS. 



Oval, depressed ; mantle large, simple, covering the head and foot ; 

 dorsal tentacles two ; clavate or conical, lamellated, retractile within 

 cavities ; gills surrounding the vent on the posterior part of the back, 

 retractile into a cavity. 



All seas. 



* 250. D. Carinata, Quoy, I.e., ii., p. 254. Oval, convex, rough, 

 keeled above ; dirty yellowish ; tentacles truncate, pediculated ; 

 branchise tuberculated. 



