BY R. ETHERIDGE, JUN. 211 



The septum of the ventral valve, when exposed by fracture, is 

 well shown, and is narrower in proportion than that of G. carbon- 

 aria, and without its abrupt forward termination, the decrease 

 being much more gradual, and the inner ridge more or less 

 sigmoidal. The dental plates are also shorter, and do not graduate 

 into the septum as in C. carbonaria. 



McCoy describes the shell as punctate, but Davidson makes no 

 remark on the subject. In the present specimens it is impunctate. 

 The interior details of the dorsal valve are wanting, and in conse- 

 quence it is impossible to throw any further light on its relation 

 to Pentamerus than the late Dr. Davidson did. 



Genus PRODUCTUS, /. Sowerhy. 



Obs. — It is always unfortunate when the palseontological appetite 

 is incited by promising material of a limited nature. Such is the 

 case with the dorsal valve of a large Productus, measuring 3 x 3 J 

 inches. The interior is exposed, displaying a large and prominent 

 septum, and a remarkably straight hinge line. From the inner 

 contour of the valve it is quite apparent that the outer was flatly 

 concave. The dendritic adductor impressions are well shown, 

 but still more remarkable are the deep long channels of the spine 

 bases, visible not only on the sides, but over the general front 

 surface of the valve. It is difficult, and somewhat hazardous to 

 speak as to specific identity on such a specimen as this, but it may 

 be P. subquadratus, Morris, or P. scabricidus. The former is met 

 with in the rocks of the Mount Britton gold-field, North Queens- 

 land, but as a rule the dorsal valves are deeper and not so wide. 



PELECYPODA. 



Genus PACHYDOMUS, Morris. 



Obs. — The greater portion of the right valve of a species allied 

 to Pachydomus globosus, Sby., sp., but probably possessing a 

 smoother shell. As regards size, its dimensions are small when 



