236 GASTROPODA. [Pectinibranchia. 



1. Melanopsis trifasciata, Gray, 1843. Plate 39, fig. 11. 



Melanopsis trifasciata, Gray, Dieff. N.Z., 263. M. zetandica, Gould, P. Bost. 

 S.N.H., ii, 1843, 225; U.S. Expl. Ex., xii, 130, f. 146. a, b. M. Strangei. 

 Reeve, Conch. Icon., f. 3. M. ovata, Dunker, Malak. Blatt., viii. 150. 

 M. trifasciata. Gray : Smith, Ereb. & Ter.. ii. pi. 1. f. 18-22 ; Hedley and 

 Suter, P.L.S. N.S.W. (2). vii, 618 ; Suter. J. de Conch., xli. 220. 



Shell ovate, rather thin, smooth, the spire very often much eroded. 

 Sculpture consisting of irregular growth-striae, very often developed 

 into folds, giving the shell an irregularly costellate appearance ; some 

 specimens are slightly wrinkled and malleated. Colour dark olive, the 

 last whorl with 1 or 3, rarely 2, chestnut spiral bands, the first above, 

 the second below the periphery, and the third at the base, the latter 2 

 a little closer together. Epidermis solid, dull or only faintly shining. 

 Spire short, conical, acute, about one-third the length of the shell ; 

 outlines straight. Protoconch conical, of 1 very rapidly increasing 

 costellate whorl. Whorls 3 to 4, very rapidly increasing, flat, the last 

 very large, slightly ventricose ; base convex, depressed upon the neck. 

 Suture superficial. Aperture large, elongately oval, sharply angled 

 above, distinctly notched below. Interior light blue, with chestnut 

 spiral bands. Outer Up simple, acute, sometimes sinuate toward the 

 base, and roundly produced beyond the end of the columella. The 

 columella is strongly callous above, the callus white near the margin, 

 yellowish-brown inside, then excavated, concavely twisted at the 

 base, and sometimes with a few short folds on the outer margin. 



Operculum obliquely striate, thin, horny ; nucleus terminal. 



Diameter, 11 mm. ; height, 18 mm. (medium-sized specimen). 

 Diameter, 17 mm. ; height, 30 mm. (large specimen). 



Dentition. Button, T.N.Z.I., xv, 123, pi. 14, f. F. 



Type in the British Museum. 



Hob. Waitangi Falls (Dieffenbach) ; Henderson, near Auckland 

 (H. S.) ; Whangarei ; River Thames ; Petane Creek, near Napier ; 

 Wanganui River ; Collingwood ; Kenepuru Sound ; Greymouth ; 

 Dunedin. 



Fam. CERITHIIDJE, Fleming. 



Animal with the rostrum broad, short, and contractile ; tentacles 

 wide apart, subulate ; eyes on short peduncles united to the outer 

 side of the tentacles. Mantle-margin with a rudimentary siphonal 

 fold in front ; gill composed of a single series of plates. Foot broad 

 and short, angulated in front. Radula long and linear; formula of 

 teeth 2+1 + 1+1 + 2. Jaws cancellated. 



Shell usually turriculated, sometimes very large, many-whorled, 

 frequently varicose, the surface usually tuberculated, spinose, or 

 costulate ; aperture siphonostome, sometimes much expanded, always 

 with a channel in front, which is more or less long and recurved ; outer 

 lip generally expanded in the adult ; columella excavated, twisted 



