ART, 4 



CAMBRIAN CONCHOSTRACA — ULRICH AND BASSLER 101 



obscure "Leperditia ebenina" of Dwight. Possibly the two are of the 

 same species, which is not improbable, since they are alike in size. 

 However, their exact relationship can not be established with the evi- 

 dence now available. 



Occurence. — Lower Cambrian (Hanfordian, division Cl6l): Han- 

 ford Brook, St. Martin's New Brunswick. 



"LEPERDITIA" EBENINA Dwight 



Plate 7, Figures 33, 34 



Leperditia ebenina Dwight, Amer. Journ. Sci., sec. 3, vol. 38, 1889, p. 144, pi. 6, 

 figs. 2-4; Trans. Vassar Bros. Inst., vol. 5, 1890, p. 104, pi. figs. 2-4. 



The collection of the United States National Museum contains but 

 a single badly crushed and incomplete example of this species. It was 

 collected by Professor Dwight and presumably belonged to the material 

 on which he based the species. Judging from the figures published by 

 Dwight none of the type specimens is in satisfactory condition. It is 

 represented as transversely subelliptical or semiovate in outline, with 

 a rather long, straight hinge, sharply defined dorsal angles, sub- 

 equally rounded ends and more gently convex ventral edge. There is 

 some indication of a wide marginal rim and the surface of the valves 

 was probably rather strongly convex. However, in the present flat- 

 tened condition of the specimens neither of these features is satisfac- 

 torily determinable. The most striking characteristic is that the pits 

 of the reticulated surface ornament beginning with very minute sizes 

 along the margins, gradually increase in size toward the middle of the 

 valve, where over a considerable space they are visible to the unas- 

 sisted eye. This peculiarity is shared by only one other Cambrian 

 species, namely, the scarcely better known Leperditia?? ventricosa 

 Matthew. As both are about equal in size, it is not improbable 

 that they represent one and the same species. Until better speci- 

 mens have been found neither can be regarded as an established species. 

 It is needless to say that they do not belong to Leperditia. 



Occurrence. — Middle Cambrian, thin bedded limestone, Stissing, 

 Dutchess County, N. Y. 



" LEPERDITIA" CAPSELLA Chapman 



Plate 10, Figure 17 



Leperditia capsella Chapman, Proc. Roy. Soc. Victoria, vol. 31, new ser., pt. 1, 

 1918, p. Ill pi. 9, fig. 4. 



The illustration of this species is included herewith to complete the 

 list of Cambrian forms, although the correct generic position can not 

 be determined at present. 



Occurrence. — Upper Cambrian, Archeocyathina limestone: Curra- 

 mulka. South Australia. 



