1872.] ETHERIDGE QTTEENSIAND EOSSILS. 339 



have of this species none x^ossesses any shell- structure ; they occur 

 in the form of casts only, and appear to abound in the Cretaceous 

 beds of Maryborough. Figure reduced |. 



Log. Maryborough. Form. Cretaceous ; horizon doubtful. 



Trigonia kasfta, Etheridge. PI. XIX. figs. 2, 2 a. 



Shell triangular or deltoid, much produced or elongated at the 

 posterior end ; anterior side truncated ; umbones prominent and 

 thick; hinge-area and teeth not preserved, save a few on the 

 posterior area. 



Obs. We possess only the cast of this shell ; and had it been 

 found in the Cretaceous rocks of Britain we should have allied it to 

 Trigonia alcpfonnis, Park., or T. caudata, Ag.; our shell, however, 

 from the umbo to the ventral margin, is much higher or deeper 

 than either of the two forms referred to. We have no means of 

 ascertaining the ornamentation upon the shell, or whether it was 

 simply ribbed, or tuberculated. I am inclined to believe that the 

 concentric folds or ribs supported tubercles upon them, as in Tri- 

 gonia scabra and T. caudata. Only one specimen has occurred ; but 

 I unhesitatingly refer it to the Cretaceous deposits ; it belongs to a 

 type not known in the Jurassic rocks. T. sanctce-crucis, Pictet and 

 Camp., much resembles this shell. C. L. Griesbach, Esq., describes 

 and figures a Trigonia, from the Umtamfuna river, Natal, which has 

 an elongated posterior end and in general shape and deltoid form is 

 much like our shell ; want of external structure, however, prevents 

 our making further comparison. 



Log. Maryboz'ough. Form. Cretaceous ; horizon doubtful. 



Ceenattjla (?) GiBBOSA, Etheridge. PI. XIX. fig. 3. 



Shell elongated, somewhat deltoid ; hinge-line thick, straight, 

 about one third the width of the shell ; umbo acute, slightly curved, 

 no impression of pallial line visible ; anterior slope appears to have 

 gaped for the passage of a byssus, as in Mytilus {but, possessing only one 

 valve, this mag be doubtfid) ; ventral margin broadly rounded and 

 flattened ; lateral margin slightly expanded ; umbonal region very 

 deep. Although I have figured this cast, I am nevertheless at a loss 

 to know where to place it ; I however refer it to the subgenus 

 Crenatula. The single muscular scar places it in the section 

 Asiphonida Integripallialia ; one specimen only, and that a cast of 

 the right valve, occurs in the collection : our shell may have some 

 affinity with Pidvinites ; but at present the nature of the hinge-line 

 and hinge-area is not known. I however suggest this. 



Much interest is attached to this singular cast ; and I trust our 

 figure will enable Australian collectors to furnish us with more 

 perfect specimens. I am disposed to regard it as a new genus ; 

 but the want of more evidence and better materials restricts me 

 from further description. Figure reduced ^. 



Log. Maryborough. Form. Cretaceous. 



Genus ? PL XIX. fig. 4. 



Shell apparently smooth, semicircular, nearly equilateral, equi- 



