147 



16. Ischnochiton ptychius, Pilsbry. 



Ischnochiton ptychius, Pilsbry: Nautilus, vol. viii., p. 53; 

 Bednall, Proc. Mai. Soc, London, vol. ii., part 4, April, 1897, 

 p. 147. 



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 Haliotidce 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 

 /. crispus. 



I. ptychius has finely striated girdle scales. 



17. Ischnochiton tateanus, Bednall, 1896. 



Ischnochiton tateanus, Bednall, Proc. Mai. Soc, London, vol. 

 ii., part 4, April, 1897, p. 147; Sykes, Proc. Mai. 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. 



/.. 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. 



Ischnochiton wilsoni, Sykes, Proc. Mai. 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 



