TILSBUY : ON THE GENUS CRTPTOPLAX. 157 



The dimensions in millimetres of two specimens having posterior 

 valves of about equal size are as follows : — 



Length of Breadth of Length of Breadth of Length 

 valve viii. valve viii. valve vi. valve vi. of animal. 



C. Gunnii ... 11-5 ... 4*7 ... 13 ... 4"7 ... 90 



C. striatns ... 11-2 ... 5*0 ... 14 ... 5'S ... 58 



The measured individuals are both alcoholic, and in apparently about 

 the same condition of preservation. The valves were measured across 

 the articulamentum at their greatest width. 



C. striatus occurs as far south as Port Jackson, while C. Gunnii 

 replaces it in South Australian waters. 1 



The mummies of Cryptoplax ordinarily to be seen in collections are 

 unsatisfactory for study, but their original colour and proportions 

 may sometimes be restored by soaking in tepid water, a little potash 

 expediting the process. 



EXPLANATION OF PLATES. 

 Plate XIV. 



Figs. 1-8. Cryptoplax Elioti, n.sp. Valves i to viii, dorsal view. Valve ii is 

 imperfect in having the sutural laminae broken, x 12£. 



,, 9. ,, ,, Lateral view of valve viii. 



,, 10. ,, ,, The animal, natural size. 



,, 11. ,, ,, Girdle spicules, x 30. 



,, 12. C. larveeformis, Burr. Valve viii of a young individual, from above. 



(No. 10,128 : Coll. Acad. Nat. Sci. Philad., Viti Is.) 



,, 13. ,, ,, Valve vii of an older specimen. (No. 77,307 : Coll. 



Acad. Nat. Sci. Philad., Apia, Samoa Is.) 



,, 14-1G. ,, ,, Valve viii of au adult. (Viti Is.) 



Plate XV. 



Figs. 17-19. C. Gunnii, Eve. Valve viii of an adult. (No. 74,553 : Coll. Acad. 



Nat. Sci. Philad., St. Vincent Gulf.) 

 ,, 20-22. ft striat/ts, Lam. Valve viii of an old specimen. (No. 10, 129 : 



CoU. Acad. Nat. Sci. Philad.) 

 ,, 23. ,, ,, Lam. Valve vii of the same individual. 



,, 24. ('. Gunnii, Rve. Integument of a young individual. x 30. 



(No. 74,554: Coll. Acad. Nat. Sci. Philad., Marino, South 



Australia.) 

 ,, 25. ,, ,, Bve. Integument of an adult. (No. 74,553.) 



,, 26. ,, ,, Eve. Dorsal view of an alcobolic specimen. Natural 



size. (No. 74,553 : Coll. Acad. Nat. Sci. Philad., St. Vincent 



Gulf, South Australia.) 



1 In his useful paper ou Polyplacophora from Port Phillip, Victoria, Mr. E. E. Sykes 

 records C. striatus (Lam.) ; but as he cites Gunnii in the synonymy, I do not 

 know which form he actually had before him. Vide Proc. Malac. Soc, 

 Vol. ii, p. 93. 



