Mr Etheridge on Fossils from Bowen River Coalfield. 287 



characterised by the presence of a short septum and a little 

 developed muscular system. On the other hand (PL XIV., f. 4a 

 and h of the same work), the silicious cast, with a very long- 

 septum and great muscular development, is a distinct and 

 separate species ; its identity will be considered further on. 



I am indebted to the kindness of Professor T. M'K. Hughes, 

 M.A., for the loan of the specimen of P. Irachythcerus from the 

 W. B. Clarke Collection of the Woodwardian Museum, referred 

 to by Professor M'Coy in his celebrated paper on the New 

 South Wales Fossils,* and also for the type of Proditctus 

 undulatus (M'Coy), from the same collection. The Cambridge 

 specimens of P. hracliythmrus do not call for any particular 

 notice beyond the fact that they show the species to be in 

 outward appearance not unlike the variety pugilis (Phill.) of 

 the European species, P. semiretimlattcs (Martin) — a peculiar 

 streaky appearance is given to the exterior of the shell by the 

 decurrent bases of the spines. With regard to M'Coy's P. 

 undulatus, Professor De Koninck-f refers it to P. hrachythwrus ; 

 but a careful examination of the type forwarded to me from 

 the Woodwardian Museum has not so thoroughly convinced 

 me of the advisability of this step as I could wish. I have 

 not seen such peculiar undulating strise upon any specimen 

 of P. hrachythccrus I have examined. 



Finally, a few words must be said on tlie subject of Pro- 

 ductus fragilis (Dana). My own impression, taken merely 

 from the description and figures of the species by Professor 

 Dana, is that P. fragilis is nothing more than a condition 

 of P. hrachythoirus. Professor De Koninck is of a contrary 

 opinion, and has furnished an elaborate description of it in 

 his recent work. J With all due respect, however, I would 

 venture to suggest that Professor Dana's description and 

 figures are totally inadequate for any palceontologist to deter- 

 mine, with anything like certainty, what is, or is not, Pro- 

 ductus fragilis (Dana). I looked forward to being able to 

 throw some light on this subject by means of a direct com- 

 parison of authenticated specimens of P. fragilis, with the 

 Morrisian type of P. Irachythcerus. Unfortunately, however, 



* Annals Nat. Hist., 1847, xx., p. 235. 



+ Foss. Pal. Kouv-Galles du Sud., 1877, pt. 3, p. 198, X Loc. ciL, p. 201. 



