Mr Mhcridge on Fossils from Boivcn River Coalfield. 309 



of Messrs Kiiifx, Davidson, and Geinitz. Airain, if I mistake 

 not, the septum has in S. Jukesii a much greater extension 

 towards the front. 



The chief point to be borne in mind when reviewing the 

 specific reLations of the present shells is, their connection with 

 those previously described under the name of aS^. Gerardi and 

 S. Clarkei. At first sidit the difference in outline between 



o 



the deltoid or quadrate form of S. Jukesii, and the oval S. 

 Clarkei, would induce separation, but when we take into 

 consideration the extreme variability of species of Stro- 

 phalosia, and the very close correspondence between the 

 massive internal characters of figs. 21 and 23 and those 

 displayed by figs. 41 and 42, I think it is just an open 

 question, whether the presence of a series of intermediate 

 forms would not necessitate the union of all in one variable 

 species ? The view here hinted at receives some support 

 from the flat exterior of the dorsal valve in both, and the 

 remarkable condition of the concentric laminae which consti- 

 tute the surface of the valves. Finally, as regards S. Gerardi (?), 

 tlie ventral valves both of it and S. Jukesii are alike, very 

 convex, but in the former the dorsal valve is very concave, 

 in the latter quite flat, except in one example, which is a 

 little inclined to the concave condition. 



It would not surprise me if eventually we have to unite 

 the shells now described as Stroijhalosia Clarkei (Etheridge), 

 >S'. Gerardi (King ?) and S. Jukesii (Etheridge, jun.), in one 

 variable species, although, as I have before said, such a pro- 

 ceeding would be premature, as the material to hand is not 

 sufficient in itself. In the meantime the subdivision now 

 made will serve for the illustration of the specimen, and can 

 be altered if occasion should arise. 



Localities. — New South Wales, Jukes Collection, Brit, 

 Mus., (?) Carboniferous, or Permian ; Tasmania, Coll. of T. 

 Davidson, Esq., F.K.S., to whom I am indebted for the loan 

 of specimens, (?) Carboniferous or Permian. 



The following is a description of the silicified Productus (?), 

 figured by Professor Morris under the name of Productus 

 h-rachythcerus (G. Sow.). 



