56 SUTER : COMMUNICATIONS FROM NEW ZEALAND. 



shows all the characters of the typical form. My largest specimen 

 has 8 whorls, the height is 25, and the diam. 12 mill., but the speci- 

 mens usually obtained have only 6 whorls and a height of 14 rnill. 



The teeth of the radula are shown in tig. 13. The central tooth 

 has cusps of the same number and size as the species, but they are 

 not united at the base. This however may be due to the young age 

 of the specimen. 



Hub. — Dredged with oysters in Foveaux Strait. Type in my 

 collection. 



The usual dimensions of T. ambiguiis for adult specimens are 40 

 X 20 mm., but sometimes real giants are met with ; in Lyttelton 

 Harbour I dredged in two fathoms a specimen measuring 55 x 34 mm., 

 which is the largest I have seen. 



Trophon patens (li. & j.). 



This species was provisionally removed from Purpura to Trophofi 

 by Mr. E. A. Smith^ on account of the Muricoid operculum. Having 

 found a living specimen I thought it to be of some interest to examine 

 the dentition, which is represented in fig. 14. The central tooth has 

 5 cusps, the mesial one is long and stout, the two distal cusps are 

 about half as large, and between the distal and mesial cup is a minute 

 denticle on each side ; the cusps are not united at the base. 



Thus the dentition also bears out the correctness of Mr. E. A. 

 Smith's classification of this species. The shell is generally smooth, 

 but extreme forms occur which have the same narrow grooves as 

 T. cheeseiiiani. Hutt. 



EXPLANATION OF PLATE IIL 



Fig. I. Khytida greenwoodi, Gray, drawn from life, nat. size. 

 ,, I a. ,. ,, ,, ommatophore, enlarged. 



,, 2. P/iacussa Jiypopolia, Pfr., abnormal teeth of radula, much magnified. 

 ,, J. Charopa bianca, Hutt., ,, ,, ,, ,, ,, 



,, 4. Charopa egesfa, Gray, jaw, much magnified. 

 ,, J. ,, ,, ,, teeth of radula, greatly magnified. 



,,6. ,, ,, ,, reproductive organs, much magnified. 



,, 7 — 9. Ptychodon ureweraensis, Sut., shell, x 10. 



,, 10. ,, ,, ,, aperture with lamellae, magnified. 



,, //. Trophon ambi^uus, Phil., teeth of radula, much magnified. 

 ,, 12. ,, ,, ,, operculum, magnified. 



,, 13. ., ,, ,, "var. puniila, Sut,, teeth of radula, much 



magnified. 

 ,1 14- ,, patens, PL & J., teeth of radula, much magnified. 



3 Proc. Mai. Soc. Lond., i, p. 57. 



