182 
ventral valve were rather strong and deeply excavated in the test (PL XI, 
Pig. 10), while those of the dorsal valve were very superfieial (PL XI, Pig. 
10«). The external surfaee of both valves must have been ornamented with 
numerous rather strong, concentric lines of growth, as the internal casts have 
preserved traces of them. 
Dimensions. — The only perfect specimen sent me is thirty-four milli- 
metres long, thirty-six broad, and twenty-six thiek. These dimensions do not 
agree with the distorted specimen deserihed and figured by MeCoy, that 
appears longer than broad because it has sustained lateral pressure during 
fossilization. 
Delations and Differences — This species is easily distinguished from 
all its congeners by its suhtrigonal form. Mr. McCoy relying on the 
defective shape of his specimen believes it to he longer than broad, and uses 
this as a characteristic to distinguish it from S. Darioinii and suhradiatus, 
which it resembles by the lateral folds ornamenting it. I have already 
remarked that this opinion is wrong, and that far from being longer than 
broad this species is on the contrary two millimetres broader than long, in 
well preserved specimens. 
Horizon and Localities. — Mr. McCoy says that this species is not 
uncommon in the sandstone of Barraha. Mr. W. B. Clarke found it at 
-Pllalong, and in a greyish sandstone about 34 miles from Newcastle, and at 
'Wollongong, New South Wales. 
Spirifee duodecimcostatus, McCoy.^ 
PL X, Fig. 12," and PI. XII, Fig. 4. 
Spirifera duodecimcostata, F. McCoy, 1847, Ann. Mag. Xat. Hist., XX, p. 234, pi. 47, 
fig. 2, 3. 
Spirifer duodecicostatus, J. D. Dana, 1849, Geol. Wilkes’ U. S. Exidor. Exped., p. G84, 
pi. 2, fig. 1. 
„ Darwmii, Idem, 1849, ibid., pi. 1, fig. 7, 8 (fig. 7a exclusa). 
This shell is slightly transverse, oval or suhrhomhoidal, gibbous, 
broader towards the middle of its length than near the hinge line. The 
^ [Spiriferina duodecimcostata. Pi. Etheridge, Junr., Geol. Pal. Q’land, 1892, p. 234, t. 44, f. 12; Spirifera 
duodecimcostata. Records Geol. Survey N. S. Wales, 1894, IV, Pt. 1, p. 34, t. 7, f. 4-8. — W.S.D.] 
^ [There is no Fig. 12 on PI. X of the original work — Fig. lift must be meant to represent 8 . duodecimco- 
stata. In our opinion the form figured is the ventral valve of a ribbed variety of Martiniopsis snbradiata, 
G. Sby.— VV.S.D.] 
