Mr Etheridge on Fossils from Boivcn River Coalfield. 311 



that I consider any identification made by means of these 

 to be in the highest degree problematical. As previously 

 pointed out, a direct comparison with the type or types 

 of P. fragilis cannot now be made, and I think it not 

 improbable that it is only a form or variety of P. hrachy- 

 thcerus (G. Sow.). 



On comparing the figures of the present Productus with 

 those of StropJmlosia Clarkei (figs. 26 and 27), one would at 

 first sight be inclined to think them identical ; but on a close 

 examination this is not so clear. It is quite true that in the 

 ventral valves of the two (figs. 26 and 46) we observe the 

 same large beak, elongated adductor scars, deep ridged cardinal 

 scars, and convex gibbous form. In the dorsal valve both 

 have a long septum, extending nearly to the front margin, 

 and the adductor scars occupy the same position. In the 

 ventral valve of S. Clarkei the thick prominent beak occa- 

 sionally overhangs the hinge line ; but in the silicified cast, 

 on the contrary, it projects some distance beyond it, even 

 allowing for the specimen being a cast (fig. 44). In the dorsal 

 valve of aS'. Clarkei the boss, or cardinal process, projects from 

 the hinge line at an angle of about 119° ; but in Productus sp. 

 it assumes the regular Productoid type, and is vertical to or 

 at rio[ht angles with the hineje line. In Strzelecki's silicified 

 Productus (?) we observe the reniform impressions, with the 

 laterally elongated, and oval or circular extremities usually 

 met with in the genus (fig. 44) ; but in S. Clarkei (figs. 21 and 

 23) these impressions assume very much more the semilunar, 

 vertically elongated scars seen in some species of Stro- 

 phalosia. Figs. 21 and 23 represent the interior of the 

 dorsal valves of aS^. Clarkei, and at /, /, are distinctly visible 

 the dental sockets for the reception of the teeth of the ventral 

 valve. Fig. 48 is a wax cast taken from the ventral valve of 

 the silicified specimen (fig. 44), and on it no sockets are 

 visible. I believe this does not arise from the absence of 

 teeth, but from their non-preservation. Figs. 44 and 45 may 

 be those of a Strophalosia rather than a Productus, perhaps 

 identical with S. Clarkei. I hope to return to this subject, 

 as I now have additional material from Point Puer, Tasmania, 

 whence probably the Strzelecki specimen came, and by means 



