WHiTEAVES ] FOSSILS OP HAMILTON FORMATION OP ONTARIO. 387 



Shell very similar to the G. Billingsi of the Corniferous limestone in 

 general shape and surface ornamentation, but differing therefrom persis- 

 tently in its much more diminutive size, and more compressed valves. 

 The largest specimens that the writer has seen are three collected at 

 Thedford by the Rev. Hector Currie in 1882, which are of the following 

 dimensions in millimetres. No 1, length 5, breadth 7 ; No. 2, 'length 

 6-5, breadth 6-25 ; No. 3, length 55, breadth 6. Average examples, 

 which appear to be adult, are not quite so large. On the other hand, two 

 of the largest examples of C. Billingsi in the Museum of the Survey 

 measure, the one 8-25 mm. in length by 1075 in breadth, and the other 

 8 mm. in length by 95 in breadth. 



Abundant at Thedford, where specimens have been collected by the 

 Rev. Hector Currie, Mr. Kernahan, Mr. Kearney, Mr. Macintosh and 

 Mr. Schuchert. 



In a previous list of the fossils of this formation the three specimens 

 collected by Mr. Currie in 1882 were regarded as a small form of C. 

 Billingsi, but the subsequent examination and study of more than a 

 hundred and fifty specimens has thrown considerable doubt on the cor- 

 rectness of this conclusion. Under the circumstances it seems desirable 

 to distinguish these little shells by a local and provisional name, as they 

 seem to bear about the same relation to the typical C. Billingsi that it 

 does to C. Horsjordi, or that C. Tetliys does to C. SappJio. 



LeIORHYNCHUS IRIS 1 Hall. 



Cfr. Leiorhynchus iris. Hall. 1867. Pal. N. York, vol, IV., p. 360, pi. 56, figs. 41-43. 



In 1895, Mr. Schuchert collected, at Thedford, a somewhat imperfect 

 specimen of a small rhynchonelloid shell, which he refers to this species, 

 but with some doubt. This specimen is No. 26,504 of the United States 

 National Museum Catalogue of Invertebrate Fossils, and two similar but 

 more perfect specimens have since been collected by Mr. Kernahan at the 

 same locality. On the ventral valve of each of these specimens there are 

 two distinct longitudinal subangular plications in the sinus and two on 

 each side or six in all, and on the dorsal three well marked plications on 

 the mesial fold and two fainter ones on each side, or seven in all. None 

 of these plications extend quite to the beak. Hall's description of L. iris 

 does not give the number of plications on either valve, but, if his figures 

 of that species are correct, there would appear to be ten or twelve plica- 

 tions on the ventral valve and ten on the dorsal. 



PUGNAX KerNAHANI. (N. Sp.) 



Shell very small for the genus, varying in marginal outline from subo- 

 vate and a little longer than wide, to subpentagonal or nearly circular 



