BY W. N. BEXSON, W. S. DUN, AND W. R. BROWXE. 



349 



ridges on either side of the sinus, whieh, liowever, are unusually coarse in charac- 

 ter. The otiier form is slightly less elongated proportionately. The length is 29 

 mm. and breadth ?■'?. mm. Locality: Shelly Ridge, S.E. of Babbinboon. De 

 Koninek states that this is one of the most abundant forms in the Middle Car- 

 boniferous Limestone. In Great Britain this form ranges throughout the zones 

 Ci-Cs. 



Spibifera PiXGUls var. eloxgata, var. nov. (Plate xx., lig. 11; Text-tig. 1.3.) 



This form differs from ,S'. pinguis in the greater elongation of the shell. Two 

 specimens have come under our notice. That illustrated in Plate xx., tig. 11, is 

 a single pedicle valve with much the same form as S. reedi (Davidson), though 

 twice the size. It has an elongate-oval outline; the hinge line is shorter than 

 the greatest width of the shell, and the cardinal angles are rounded. The beak 

 is of moderate size and strongly incurved over a triangular delthyrium. The 

 shell is smoothly convex with a broad medial sinus extending into a tongue-like 

 projection of the margin. On either side are about ten low, rounded ribs; coa- 

 eentrie lamellar growth lines cross the sinus near the margin. The other, shown 

 in Text-figure 13, is even more markedly elongate, and somewhat distorted in out- 

 line. The shell has been largely removed but sutticient remains to show that the 

 ornamentation was much finer than in the first specimen, about twenty ribs occur- 

 ring on one side of the mesial fold on the brachial valve, and the ornamentation of 

 the pedicle valve appears to have been as fine. A few concentric growth lines 

 are present on each valve. The dimensions are: — 



Fig. 11. Text-fig. 13. 



Length in millimetres 34 24 



Breadth 26 19 



Length of hinge line 1.5 12 



Total thickness — 18 



Depth of pedicle valve 11 10 



The first of these forms was obtained by Benson in tiie south-east of Babbin- 

 boon, and is in the collection of the University of Sydney. The second (Specimen 

 No. F4360 of the Geological Survey Museum, N.S.W.) was obtained by Cullen 

 from Reserve 121. Parish of Moorowarra. 



Text-fig. 13. — Spirifera pinguis rar. elongala, 

 var. nov. Moorowarra. 



Text-&g.l4,.—Posidonie//a ? spp. 

 indet. Babbinboon. 



