THE 



GEOLOGICAL MAGAZINE. 



No. XXIX.— NOVEMBER, 1866. 



OiaiC3-IIsr.A.Xi -A-iaTIOLIEBS. 



I. — On the Australian Tertiary Species of Trigonia. 



By Frederick M'Coy, F.G.S. 



Professor of Natural Sciences in the Melbourne University ; Director of the National 

 Museum of Victoria ; False ontologist to the Geological Survey, etc., etc. 



AS I have prepared descriptions of nearly all tlie fossils of Vic- 

 toria collected by the Geological Survey under Mr. Selwyn for 

 some years, I have been urged to make a preliminary publication in 

 the Geological Magazine of some of the more remarkable forms, 

 and I now forward my descriptive note of the two Tertiary Trigonice, 

 on account of Mr. Jenkins' paper in the May number of this Journal, 

 in which one of them is referred to the recent T. LamarcTcii. I feel 

 assured that if Mr. Jenkins will look at the edge along the ribs, 

 towards the beak of a recent specimen of T. Lamarchii and my 

 T. acuticostata from the Tertiary beds, he will at once appreciate 

 the distinctive form of the ribs which I point out and figure in the 

 annexed woodcut. 



Fig. 1. — Trigonia acuticostata, M'Coy. Fig. 2.^Trigonia Lamarckii, Mathn. 



Older Pliocene, &c., Victoria, South Recent Australian Seas. 



Australia. 



Description of New Species. 



1. Trigonia semiundulata (M'Coy). 



Sp. Ch. Eotundato oblong, little longer than deep, moderately 

 convex, anterior and ventral margins broadly rounded, posterior 

 margin nearly straight, abruptly truncated, forming an angle of 

 120° with the hinge line ; posterior slope flattened and radiated 

 with about ten or eleven strong obtusely rounded ridges, separated 

 by rather wider flattened spaces, and crossed by lines of growth 

 near the margin, closer and spinulose near the beak, and followed on 

 the lunule close to the hinge-line by six or seven much smaller 

 spinulose ridges ; middle and anterior portions of the valves covered 

 with narrow rounded, slightly undulating ridges, nearly parallel 



YOL. III. — NO. XXDC. 31 



