CANADIAN FOSSILS. 95 



This Trenton form, which I have termed L. Canadensis, var Joseph- 

 iana, may possibly be the same as Conrad's L.fabulites ; if so, his name 

 has priority. 



/. Var. Anticostiana. 



Plate XI. Fig. 17. 



A piece of light-grey limestone (of the upper portion of the Hudson 

 River group) from East Point, Anticosti, bears on its weathered sur- 

 face encrinital ossicles and eleven separate valves of a Leperditia of 

 different sizes ; there is besides a separate perfect carapace of the same 

 form, half an inch long, if inch broad, and ^\ inch thick). These 

 specimens have a rather short hinge-line, a w^ell-marked ocular 

 tubercle, and a muscle-spot visible only by its slightly darker tint. In 

 some instances these valves appear to have a peculiar delicacy of make 

 and substance; they slope rapidly from the central convexity; the 

 ends of the carapace are thin, and the overlapping part of the rio-ht 

 valve is distinctly central and neatly curved. This form differs from 

 that of St. Joseph's in having a shorter hinge-line and a more promi- 

 nent eye-spot; in the apparent absence of external radii to the muscle- 

 spot: in the somewhat more delicate substance of the valves ; in the 

 lesser thickness of the carapace, in its attenuated edges before and 

 behind, and in the symmetrical curvature of the overlapping ventral 

 edge. 



This neatly shaped Leperditia from Anticosti more nearly resembles 

 its almost gigantic allies of Sweden* than do any other American 

 Leperditice that I have seen. Still it is not without good points of 

 relationship with L. Canadensis, and I have provisionally termed it 

 L. Canadensis, var, Anticost.ia7ia. 



The St. Joseph's form more nearly resembles the large varieties of 

 Leperditia, Canadensis (pi. xi. figs. 11 and 12) than do the Anticosti 

 specimens ; and as I did not feel authorized to separate specifically 

 the little Grrenville varieties, that from Louck's Mill, and that of 

 Allumette, neither can I at present regard these com]3aratively 

 large and well-grown specimens as belonging to another specific type. 



Mr. Salter having lately favoured me with better specimens of 

 the Leperditia alta, from Wellington Straits, than I had previously 

 seen, I am enabled to point out, that though in size and general form 

 the Arctic L. alta much resembles the Leperditice from Louck's Mill, 

 Pauquette's Eapid, St. Joseph's, and Anticosti, it has a thinner 

 shell, and a distinct muscular spot, with vascular radii ; and further, 



* Annals of Natural Historj', 2nd series, vol. xvii. p. 85, pi. 6. 



