147 
16. Ischnochiton ptychius, Pilsbry. FeLi Y x 
53 
Ischnochiton ptychius, Pilsbry: Nautilus, vol. viii., p. rf 
Eeon ey Proc. Mal. Soc., London, vol. ii., part 4, April, 1897, 
p- " 
It is often placed among crispus, but as a rule is found 
in much deeper water. I have specimens from Robe, Cape 
Jaffa, Second Valley, Normanville, Marino, and Southern 
Yorke Peninsula. Good specimens were taken by Mr. A. R. 
Riddle on broken Haliotide at Marion Reef, and also in a 
deep rock pool at Black Hill, near Port Moorowie. The strong 
serrations at the sutural margins of the valves, mentioned by 
Mr. Bednall, are plainly distinguishable in some specimens. 
In others they are missing, although taken at the same spot 
and similar in every other particular. 
“It is a small oval pink-tinged shell, with wrinkled stria- 
tions on the dorsal areas, and somewhat coarse concentric 
sulcations on the lateral areas, which are strongly serrated at 
the sutural margin.” 
It is somewhat difficult for a beginner to separate it from 
I. crispus. 
I. ptychius has finely striated girdle scales. 
17. Ischnochiton tateanus, Bednall, 1896. FLe ada 
Ischnochiton tateanus, Bednall, Proc. Mal. Soc., London, vol. sf 
ii., part 4, April, 1897, p. 147; Sykes, Proc. Mal. Soc., London, 
vol. ii., part 2, July, 1896, p. 87. 
It may be distinguished by its form. In well-preserved 
specimens the width is nearly two-thirds of the length, and 
the fine serrations on the posterior edge of the lateral areas 
of the median valve are distinctly seen in most of the 
specimens. 
I. tateanus is rarely found near the shore. It is a deep- 
water species. Dr. Verco has dredged several in St. Vincent 
and Spencer gulfs, and valves have been taken at St. Francis 
Island in 19 fathoms of water. A beautiful specimen was 
taken by Mr. F. L. Saunders at Marino. It is a pale-chocolate 
on the dorsal area, throughout the valves, and the lateral and 
pleural areas of the second, sixth, and seventh valves are 
creamy-white. 
17a, Ischnochiton wilsoni, Sykes, 1896. FLEX 
Ischnochiton wilsoni, Sykes, Proc. Mal. Soc., vol. ii., part 2, 
July, 1896, p. 89. 
One specimen dredged by Dr. Verco and one procured 
by Mr. Matthews are probably all that have been found in 
South Australian waters. The writer has one specimen 
9x5 mm. from Marino (?). In this sample the granulations 
F2 
