178 Transactions. — Zoology. 



Hah. Mount Somers, Canterbury (Dr. von Haast), on limestone 

 cliffs. 



Distinguished by its smooth shining surface and brown and white 

 bands. Its generic position must remain doubtful until the dentition is 

 known. 



Pfeiffekia (?) cressida, ii. s. PL ix., fig. x., and pi. xi., fig. n. 



Shell turbinate, depressed, thin, translucent, striated, umbilicus covered ; 

 fulvous horny. Spire convex ; whorls 5%, slowly increasing, rounded, 

 shining, finely irregularly striated or plaited : suture impressed : umbilicus 

 very narrow, covered by the peristome : aperture slightly oblique, Innately 

 rotund ; peristome thin, regularly arched, the columellar margin slightly 

 thickened and reflected over the umbilicus. Greatest diameter -48, least 

 •88 ; height -33 inch. 



Bob. Southland (G. M. Thomson). 



Jaw arcuate, flatly ribbed, the ribs indenting both margins. 



Dentition, 35-1-35 ; varying from 32 to 37. Laterals about 17. 



Central tooth rectangular, twice as long as broad ; the reflexed portion 

 half the length of tbe base, slightly constricted on each side, and with a 

 minute cutting point. Laterals with the reflexed portion bicuspid, the 

 inner cusp carrying a cutting point which gets longer further from the 

 centre ; outer cusp notched in the middle. Marginals broader than long 

 with several cutting points ; on the inner marginals the two points at the 

 inner corner are larger than the others ; the outer marginals are irregular 

 and the points disappear altogether. 



In this species the shell is seen, under the microscope, to be finely 

 obliquely reticulated, the crossing stria? having diagonal directions. I 

 formerly mistook it for H. guttula, but in that species the shell is described 

 as very smooth, with an inconsiderable, sub -margin ated suture, and the last 

 whorl as callous beneath, in all which points it differs from our species. 

 It is doubtfully referred to the genus Pfeiferia as the animal is not 

 known. 



GeRONTIA CORDELIA, n. S. 



Shell sub-discoidal, widely umbilicated, striated ; colour pale horny, 

 marbled with reddish brown and covered by a shining yellow epidermis. 

 Spire convex ; whorls 4^, slowly increasing, rounded, with tolerably regular, 

 rather crowded, and rather coarse stria? of old growth-lines ; suture im- 

 pressed ; umbilicus broad, conical, showing all the whorls, but not gra- 

 dated; aperture slightly oblique, sub-circular; peristome thin, right margin 

 descending, columellar margin rapidly ascending but not vertical, the two 

 margins not approaching. Greatest diameter *32, least *27; height -18 

 inch. 



