352 GASTROPODA. [Pectinibranchia. 



the second whorl relatively much enlarged, bulbous ; all smooth. 

 Whorls 10, regularly increasing, flat, the last slightly angled at the 

 periphery. Suture distinct, not impressed, irregularly indented on 

 the lower part of the shell. Aperture small, vertical, pyriform. regu- 

 larly arched below. Outer lip sharp, very slightly convex. Columella 

 short, arcuate. Inner lip forming a slight callosity on the pillar and 

 parietal wall, rounded off at the base toward the basal lip. Opff- 

 culum unknown. 



Diameter, 3mm.; height, 13mm. Aperture breadth. 1-5 mm. ; 

 height, 3 mm. 



Animal unknown. 



Type in the Dominion Museum. Wellington. 



Hob. Off Great Barrier Island, in 110 fathoms (type). 



Remark. The mucronate tip of this species somewhat recalls 

 E. Coxi, Pilsbry. (C. Medley.) 



Tribe 2. HETEROPODA. 



These are free-swimming Tcenioglossa, with the foot flattened 

 laterally and the otocysts situated near the cerebral ganglia. There 

 are no mandibles, and the intestine is short. All the Heteropoda 

 are pelagic, and are much modified in adaptation to this mode of 

 existence. The foot is very large, and has the form of a fin com- 

 pressed bilaterally ; it bears, in the male at least, a sucker at its ventral 

 aspect. The visceral sac or " nucleus " and mantle form a progres- 

 sively smaller and smaller part of the mass of the body, but the head 

 always remains large, and forms a cylindrical snout. The eyes are very 

 large and highly differentiated in structure ; they are placed at the 

 sides of the cerebral ganglia and at the bases of the tentacles when 

 the latter organs exist. The alimentary canal is furnished with a 

 protractile pharynx containing a characteristic taenioglossate radula, 

 with very powerful lateral and marginal teeth. 



They are transparent, and are generally found in dense bands 

 in warm and temperate zones, swimming slowly in a reversed position 

 that is to say, with the foot uppermost. They are all carnivorous. 



Fam. ATLANTID.2E, Rang. 



Visceral sac and shell spirally coiled in one plane ; foot divided 

 transversely into two parts, the posterior part bearing an operculum 

 with a sinistral coil, while the anterior part forms a fin provided with 

 a sucker. Radula with the central tooth tricuspid, sometimes only 

 with a median tooth ; inner lateral tooth large, bicuspidate, with an 

 inner obtuse process ; the other laterals are curved and aculeate. 



Genus 1. ATLANTA, Lesueur, 1817. 



Shell discoidal, fragile, transparent, compressed, carinated through- 

 out, and capable of containing the whole animal ; protoconch dextral. 



