<S8 PKOCEEDINGS OK THE ACADEMY OF [1894. 



Academy collection, taken by Dr. Cox at Bun(lal)nrg, Queen.'<- 

 laud. 



Genus ONITHOCHITON Gray. 



Two species or at least forms of this genus are represented in the 

 collections made by Dr. Cox at Port Jackson and Port Hacking. 

 The relations of 0. Lyellil Sowb., (jiierclnus Gld. and nir/iilosiis 

 Aug. are peculiarly perplexing, and more material than is before me 

 is required for a satisfactory revision of the group. 



0. rugulosus Angas. 



Port Jackson and I'ort Hacking, (Cox!). In this form tlie lateral 

 areas are transversely rngose, and the pleura have fine, close irregu- 

 lar riblets, converging toward the ridge. 



0. quercinus (Jould. 



Port Jackson (Cox!). 



I take this to be the form having the central areas nearly smooth, 

 with som(> riblets toward the outer edges of the pleura. Probably 

 intergrades with the preceding. 



Explanation of Plates. 



Plate U. 



Figs. 1 to 6. AcanlhdcJtUc^ yraiiodriatitc Pilsbry. 



Fig. 1. Dorsal view of valve vii. 



Fig, 2. Dorsal view of valve viii, sutural lamina' broken. 



Fig. 3. Ventral view of valve viii, sutural lamina) broken. 



Fig. 4. Posterior view of valve viii. 



Fig. 5. Lateral view (profile) of valve viii. 



Fig. H. Sculpture of tlie middle of side area of an intermediate 



valve, X 22. 

 Figs. 7 to 11. Acanthochites Bednalll Pilsbry. 

 Fk;. 7. Dorsal view of valve vii. 

 Fig. 8. Dorsal view of valve viii. 

 Fig. 9. Posterior view of valve viii. 

 Fig. 10. Lateral view of valve viii. 

 Fig. 11. Sculpture of side area, x 22. 

 Figs. 12 to 15. Acanthorhlten retrojactHx Pilsbry. 

 Fig. 12. Dorsal view of an intermediate valve. 



