Neojanac/(x.\ GASTROPODA. 281 



1. Neojanacus perplexus, Suter, 1907. Plate 15, figs. 15, 15a. 



Neojanacus perplexus, Suter, T.N.Z.I., xxxix, 2(56. Genus (?), Murdoch and 

 Suter, T.N.Z.I., xxxviii, 1905 (1906), 301, pi. 27, f. 52-54. 



Shell small, flat, convex when young, of very variable shape, mostly 

 elongately oval, the posterior end with a broad inward cuive. Sculp- 

 ture consisting of numerous small rounded and irregularly spaced 

 concentric growth-periods, more distant anteriorly. Colour whitish. 

 Epidermis very thin, horny, easily rubbed off. Protoconch terminal, 

 distinctly marked off, smooth and polished, cap-shaped, with a slightly 

 flattened rim-like margin ; it consists of one turn, somewhat oblique 

 to the major axis. The margins slightly laminated, and usually with 

 an upward curve, thus giving the dorsal surface a slightly concave 

 aspect. Lower surface porcellanous, highly polished, with a horseshoe- 

 shaped muscular impression, open in front, and extending over nearly 

 half the length of the shell. 



Breadth, 4-66 mm. ; length. 7-76 mm. (type). 



Animal unknown. 



Type in the Dominion Museum, Wellington. 



Hab. Off Great Barrier Island, in 110 fathoms (type) ; Port 

 Pegasus, Stewart Island, in 18 fathoms (Captain Bollons) ; Bounty 

 Islands, in 50 fathoms (Captain Bollons). 



Remark. This shell, no doubt, lives in the aperture of other shells, 

 like Crepidula contorta, Q. & G. 



Fam. HIPPONICIDJE, Fischer. 

 AmaltheidcB, Dall. 



Animal without a foot, properly so called ; adductor muscle fixed 

 to the interior of the shell above, and below either to the substratum 

 excavated in the surface of the body on which the mollusc is attached 

 or to a ventral calcareous opercular-like piece which completely closes 

 the aperture ; inferior surface of the body encircled by a sort of ventral 

 mantle with papillary margins, resembling the dorsal mantle, and 

 morphologically corresponding to the epipodium ; muzzle long, deeply 

 incised, and terminated by 2 lateral lobes ; tentacles long, subulate, 

 the eyes sessile towards their base ; a spatuliform growth below the 

 neck. Radula 2+1 + 1+1-1-2, the central tooth subquadrangular, 

 the margin pectinated, the central cusp longer ; lateral teeth with 

 denticulate margins ; marginals narrow, curved, denticulate. 



Shell conical, peristome simple, with or without an internal process 

 attached at the apex, but an opercular piece normally forms the base 

 to the shell, and is soldered to the surface of the body on which it lives 

 attached. 



The HipponicidcB are such strange molluscs that they have been 

 classed with the Rudistes by Sowerby and with the Brachiopods 

 by Morris. They appear to be formed by two valves, one dorsal, the 

 other ventral, but in reality the ventral valve is a curiously modified 

 operculum, secreted by the epipodium. The embryos have a spiral shell. 



