PTKROPODA. 5 



FAMILJT NAUTILUS. 



Shell spiral or straight ; body chamber large ; siphon central or 

 sub-central. 



NAUTILUS. 



Shell involute or discoidal, few whorled ; septa straight or siuu- 

 ated ; siphon central. 



Chinese Seas. Indian Ocean. 



11. N. pompiliuS, Lamark, -&\.,p. 321. Shell white, with fawn- 

 coloured transverse chevroued bauds ; coated internally with mother 

 of pearl. Large. 



Taurauga. Broken specimens are occasionally picked up on the 

 coast. Indian and Pacific Oceans. 



Class Pteropoda. 



Head more or less distinct ; eyes none ; mouth often furnished 

 with cup-shaped appendages ; fins on the sides of the mouth or neck. 

 Body ovate or roundish, often enclosed in a thin translucent shell. 



Animal free, floating on the surface of the sea. 



FAMILY HYALLIXE. 



Body enclosed in an elongate or globular thin shell ; head not dis- 

 tinct ; fins two, large ; gills internal. 



HYALEA. 



Shell globular, translucent ; mouth narrower than the cavity, with 

 a lateral slit on each side ; dorsal plate produced into a hood ; pos- 

 terior extremity tridentate. 



Atlantic. Mediterranean. Indian Ocean. 



1. H. affillis, D'Orb; Cavoliiia qffinis, Gray, Cat. Ptr., Brit. 

 Mus., p. 7. Shell inflated in front, flattish behind, broader than high, 

 finely transversely striated on the upper anterior portion, almost 

 smooth, below and on the back ; posteriorly three spiued, the lateral 

 ones short, the middle one slightly reflexed ; dorsal lip produced, with 

 three broad rounded ribs, which run along the back towards the median 

 spine. Brownish. 



Chatham Islands. 



FAMILY DENT ALIID JE . 



Shell tubular, calcareous, symmetrical, open at each end, attenuated 

 posteriorly, smooth or longitudinally striated ; aperture circular, not 

 constricted. 



DENTALIUM. 



Posterior opening entire. 

 Widely spread. 



2. D. pacificum, sp. nov. Solid, tapering, slightly curved, 



