Note on Arctic Palaeozoic Fossils. 263 



Leperditia phaseoltts (Hisinger) [Fig. 4]. 



18.31. Gytherina phaseolus, Hisinger, Anteckn. Phys. Geogn., vol. v., pi. 8, fig. 3. 

 1S91. Leperditia phaseolus, Jones, Geol. and Nat. Hist. Survey of Canada, Contrib. to 

 Micro-Palaeontology, p. 85, pi. 13, figs. 7, 8. 



Of common occurrence are specimens agreeing with this species. In 

 the left valve figured (Fig. 4) the length is 11 mm., the hinge 7"5 mm., 

 and the height 65 mm., these measurements agreeing with those given 

 by Jones for the Canadian representatives of L, phaseolus. 



Leperditia aff. balthica var. guelphica Jones [Fig. 5]. 



Several specimens of a large Leperditia possess the anterior tapering 

 and the salient dorsal angles of Leperditia balthica var. guelphica Jones 

 (op. cit. p. 80, pi. 13, figs. 12, 13), from which, so far as the materials show, 

 they differ in being relatively more elongate. The dimensions of the 

 specimen figured (Fig. 5) are : length 10 nun. ; hinge, 8 mm. ; height, 

 5*75 mm. 



Leperditia cf. coxa Jones [Fig. 7]. 



A few carapaces and moulds differ from the Leperditia; described 

 above in being much higher relatively to their length, and in being 

 apparently without eye-spot. These characters give this form a marked 

 resemblance to Leperditia ca?ca Jones (op. cit. p. 88, pi. 12, figs. 6, 7, 9), 

 from which it differs in having a relatively longer hinge-line. 



EEMAEKS. 



Of the species described or enumerated in the foregoing notes, the 

 series embedded in the foetid limestone and the slabs with Brachiopods 

 ami Ostracods are clearly of Niagaran (Upper Silurian) age. 'at many 

 data are still wanting without which it would be hazardous to n fer the 

 assemblage witli absolute certainty to any definite formation. Yet the 

 presence of Stroniatoporids (?) and numerous Cephalopods, large TTalysites, 

 and faintly -ribbed Spirifer crispus coupled with the occurrence of 

 Pycnomphalus solarioides and Ostracods allied to Guelph species, suggest 

 that this portion of the collection was obtained from strata belonging to 

 the Guelph, viz., the uppermost member of the Niagaran. If the bed 

 which yielded the abundant shells of Gasteropods of Catozone type was 

 ever found to be closely connected with the strata from which the bulk 

 of the collection is derived, the presumption that the group belongs to 

 the Guelph would then be strengthened, since an abundance of Gasteropods 

 is one of the characteristic features of that formation. However, as 

 conclusive evidence could only be secured by the record of certain 

 vol. xviu. 2a 



