220 REcoRns OP the Australian museum. 



The occurrence of fossils in these beds was first reported by- 

 Mr. H. y. L. Brown, the known thickness then being four 

 hundred feet.^ 



Tlie characters of the shell so freely dispersed in this 

 deposit are unfortunately, with two e.xceptions indefinite. In 

 outline it is transversel}' oblong, not unlike some compressed 

 TeUince. The valves were closed and generally compressed, 

 with an apparent absence of anterior and posterior slopes, the 

 anterior ends rounded and the posterior slightly subtruncate. 

 I cannot detect any trace of hinge teeth, and am therefore 

 constrained to regard the shell as edentulous. Both the 

 adductor scars are faint, and appear to be much elongated. 

 The two more definite features, previously referred to, are the 

 rugged exterior, and the papilose nature of the test interior on 

 the sub-umbonal region. The coarse concentric laminae of the 

 exterior succeed one another with rapidity, but at irregular 

 distances ; fragments can at once be recognised by these 

 features. 



My inability to refer this shell with certainty to any genus 

 of bivalves occurring in the Queensland Ci'etaceous System, or 

 in the Australian for the matter of that, is to be regretted be- 

 cause I feel assured that could the " Journal " of the Mount 

 Wilson Well boring be consulted this mollusc would be found 

 to indicate, or mark, an horizon, just as readily and emphati- 

 cally as does an equally obscure little bivalve 1 described 

 from southern Queensland as Pachydoinella chntiis,^ and for a 

 similar purpose. 



As a matter of fact, I can see very little difference, with the 

 limited information at my disposal, between the present 

 bivalve and that just referred to, with the exception of that of 

 outline and size. As P. chat us was coined in a great measure 

 as an aid to the field surveyor, so in this instance I suggest 

 the name of P ? fiesta? 



'•> Brown — hoc. cit., p. 725. 



'i Etlieridge— Rec. Austr. Mus., vi., No. 5, 1907. p. 325, pi. Ixii., 

 figs. 4-8. 



TTtecTTos — that which is pressed. 



