296 Proceedings of the Royal Physical Society. 



to S. Gerardi, with the concave dorsal valves, may, after all, be 

 one and the same. I am led to this impression by the otherwise 

 general resemblance of the shell structure, habit, and co- 

 occurrence. At present I am in this difficulty — on the one 

 hand we have a series of dorsal valves all flat, and no ventral 

 valves attached (= S. Clarhei) ; on the other hand a number 

 of bivalve examples, with very concave dorsal valves (? = S. 

 Gerardi)y but all from the same localities, and with many 

 points of minute structure the same — Are they identical? 

 I am afraid the question must remain at present an open one, 

 as the material to hand is not sufficient to solve the problem. 

 The more deltoid form of S. Gerardi, in particular the dorsal 

 valve, would hardly be sufficient to found a separation on, 

 more especially as it is not constant, but a gradation in out- 

 line exists, which would, in all probability, in a series of 

 specimens, gradually lead up to the oval or transversely 

 elongated outline of S. Gerardi. The same remarks apply to 

 the ventral valve, for the limited number of specimens of >S'. 

 Gerardi known renders it difficult to assert what would be 

 the average form of this valve. It may be oval, as in the 

 type specimen, or there may be a gTadation towards the 

 less regular outline of the Australian shells I have referred 

 to it. 



Should my surmise as to the identity of >S'. Gerardi and S. 

 Clarhei ultimately prove correct, my father's specific name 

 will of course have to be abandoned, that is to say, presum- 

 ing the identity of the Queensland shells with King's S. 

 Gerardi to be correct. 



In his description of S. Gerardi Professor King does not 

 mention the existence of spines on the dorsal, but I find, on 

 a close examination of his typical specimen, what appears to 

 be the bases of insertion of the spines. 



Log. and Horizon. — Pelican Creek, five miles north of 

 Sonoma Station; Pelican Creek, opposite Palmer's Old 

 Station; Bowen Paver, between Traverse Stations 25 and 

 26 ; Parrot Creek, eight miles up (Marine Series of Bowen 

 Pdver Coalfield, Nos. 12, 23, 25, 26, 29, 31, 34, 68, and 157, 

 etc.). 



Collector. — E. L. Jack, Esq. 



