352 nEOLOGY AXD PETROLOGY OF THE GREAT SERPEXTINE BELT OF X.S.W., 



Lower Limestone Series iu Scotland, hut not in the Caleit'erous SauJsu ue (31), 

 In England antl Ireland it ranges between the zones Si and Di. 



Semixttla subtilita (Hall). (Plate xxi., figs. 2, 4, 5.) 



Terebratida subtilita, Hall (In Stransburg), Explanation of the Valley of the 



Salt Lake of Utah, 1852, p. 409, t. 2, f. 1 a, b, 2 a, b, c; Davidson, Brit. 



Carb. Brach.. p. 18, t. 1, f. 21, 22; Seminula subtilita, Hall aad Clarke, 



Pal. New York, viii., pp. 93-98, t. xlvii., f. 17-31. 



This form was the first example of this widespread genus to be recognised in 



this State, but it has since been recognised in the beds at Gosforth, which are 



probably transitional between the Burindi and Lower Marine Permo-Carboniferous 



Beds (4). The species is protean, and "one feels at first disinclined to include 



under the same specific designation the broadly ficiform, the narrow elongate, the 



sinuate, non-sinuate and tri-lobed forms, which are customarily thus referred, 



but the very abundant material shows the impossibility of separating them." 



(Hall and Clarke, op. cit., p. 95). Our form is a very neat shell. The margin is 



smooth, non-sinuate, and the test is ornamented by fine radial striae and broader 



concentric bands with a few irregular growth lines. Its length is 18 mm. ; breadth, 



25 mm.; hinge line, 19 mm.; total thickness about 16 mm. It was obtained by 



Mrs. Scott in the shelly ridge in the south-east of the parish of Babbinboon, and 



now is in the collection of the University of Sydney. 



This form is widely developed in the Upper Carboniferous beds in the United 

 States, but is found rarely in the St. Louis Limestone belonging to the Upper 

 portion of the Mississi]ipian System, the American e<|uivalent of the Visean For- 

 mation (33). In Belgium, however, it descends to the Tournaisian, according to 

 De Koninck, as cited by Davidson (31, p. 219). 



PELECYPODA. 



SaxguikoIvITe.s triraiuatus, sp. nov. (Plate xxiii., fig. 8.) 



Sanguinolites, McCoy, Synop. Carb. Limestone Foss., Ireland, 1844, p. 47; Brit. 

 Pal. Foss., Fasc, ii., 1852, p. 27ti. 

 The shell is very elongate, the beak anterit)r and the lower posterior margin 

 projects beyond the hinge line. It is characterised by the presence of three 

 obtusely-rounded earinae, extending from the umbo to the posterior margin. It is 

 also marked by numerous delicate concentric growth lines. It differs from 6\ 

 tricostata (De Koninck)*, which is the most nearly allied form, in that our form is 

 much narrower and the cariiiation is less pronounced than in the Belgian form 

 (which is found in the Visean Series). The dimensions of S. triradiata are: 

 Height, 10 mm. ; length, 28 mm. ; thickness, 25 mm. The species is based upon 

 Specimen F. 4584 of the collection of the Geological Survey, obtained by Cullen 

 from the ))arish of Moorowarra, south of Somerton. 



Saxgi'ixolites sp. ixdet. (Plate xxiii., fig. 11 ) 



This form docs not appear very closely similar to any of the forms we luive 

 seen figured, but is not sufficiently well preserved for specific description. It has 

 a carina forming a low rounded ridge except near the margin of the shell, and 

 another running a short distance below it, commencing as an angular ridge near 

 the umbo, but fading out into the general curve of lower posterior margin. 

 •Faune Calc. Carb. Belg., v., 1885, p.84, t.l5, f.l5. 



