200 GASTROPODA. (Pectinibranchia. 



1. Rissoa Hamiltoni, Suter, 1898. Plate 12, fig. 1. 



Rissoa Hamiltoni, Suter, P. Mai. S., iii, 2, f. 4 in text. 



Shell minute, ovate, rimate, costate. Sculpture consisting of rather 

 distant rounded axial riblets, about 14 on the last whorl ; they 

 are stopped on it by a spiral thread starting from the suture, leaving 

 the base smooth ; interstices broader than the riblets, smooth. Colour 

 dirty-white or cinereous ; there is sometimes a rufous band encircling 

 the upper whorls above the suture, and extending on the body-whorl 

 to within a short distance from the peristome. Spire elevated conic, 

 about twice the height of the aperture, outlines slightly convex. Proto- 

 conch papillate, brownish, of 1| smooth and convex whorls. Whorls 6, 

 regularly increasing, convex ; the base flatly rounded. Suture im- 

 pressed, margined by a fine thread. Aperture vertical, rotundly ovate. 

 Peristome continuous, sharp. Columella oblique, rufous, rather con- 

 cave, subtruncate at the base. Umbilicus marked by a very narrow 

 chink. Operculum unknown. 



Diameter, 1-5 mm. ; height, 2-5 mm. 



Dentiton unknown. 



Type in my collection. 



Hob. Lyall Bay, in sand, type (A. Hamilton) ; Titahi Bay (Miss 

 Mestayer) ; Foveaux Strait ; Maloney's Reef, Hauraki Gulf (H. S.). 

 Banks Peninsula (Iredale). 



Remark. In young specimens the riblets extend over the base. 



2. Rissoa Huttoni, Suter, 1898. Plate 12, fig. 2. 



Rissoa nana, Button, C.M.M., 28, not of Philippi. R. Huttoni, Suter, 

 P. Mai. S., iii, 2. Barleeia nana, Butt,, M.N.Z.M., 81. 



Shell very small, oval, imperforate, costate, white. Sculpture con- 

 sisting of equidistant axial rounded riblets, about 25 on the 

 penultimate whorl, usually getting obsolete below the periphery of 

 the last whorl ; interstices of about the same width as the riblets, 

 smooth. Colour white or yellowish. Spire elevated conic, higher 

 than the aperture, outlines slightly convex. Protoconch small, papil- 

 late, of 1| smooth convex and polished whorls. Whorls 5, regularly 

 increasing, convex ; base rounded. Suture impressed. Aperture ovate, 

 angled above. Peristome continuous, somewhat thickened. Basal lip 

 slightly expanded. Columella arcuate, but little expanded. Umbilical 

 area with a small narrow impression. Operculum unknown. 



Diameter, 1-25 mm. ; height, 2-5 mm. 



Dentition not known. 



Type in the Dominion Museum, Wellington. 



Hab. Stewart Island (type) ; Port Pegasus, Stewart Island, in 

 18 fathoms (Captain Bollons) ; Otago Heads, dredged (A. Hamilton) ; 

 Whangaroa Harbour (C. Trail!) ; near the Snares, in 50 fathoms 

 (Captain Bollons). 



