TWO UNDESCRIBED PELKCYPODA — ETHERIDGE. 



205 



For the microscopic sections of the wood I am indebted to 

 Messrs. P. Crawford and H. Gooch, of the Geological Laboratory, 

 University of Sydney. 



2. The Occurrence op Pholadomya. 



Genus Pholadomya, G, B. Soiverby, 1823. 

 (Genera of Shells, No. 19). 



Pholadomya terra-regin^, sp. nov. 

 (Fig. 21). 

 Sp. Char. — Cast transversely elongate, oblique, inequilateral in 

 the extreme, apparently equi valve, attenuating in thickness pos- 

 teriorly. Cardinal margins straight, with a short circumscribed 



Fig. 21. 



false area. Ventral margins obliquely rounded from beneath the 

 umbones downwards, swelling out at a point slightly posterior to 

 the middle. Anterior ends practically absent. Posterior ends 

 (imperfect in specimen), but probably narrow and obtusely pointed, 

 judging by the lines of growth ; greatest convexity of the valves 

 immediately posterior to the umbones; posterior slopes somewhat 

 flattened; diagonal ridges rounded. Umbones absolutely anterior, 

 terminal, incurved, contiguous, and depressed. Sculpture of con- 

 centric rugse bearing finer parallel lines, the former separated by 

 valleys of equal width, the valves crossed diagonally, in the centre 

 only, from the umbones to the ventral margins by a few equal 



