Palaozoic Bivalved Entomostraca. 341 



comparatively large and well-grown specimens as belonging to 

 another specific type. This Trenton form, which I propose to 

 term L. Canadensis, var. Josephianay may possibly be the same 

 as Conrad^s L. fabulites ; if so, his name has priority. 



The neatly shaped Leper ditia from Anticosti more nearly 

 resembles its almost gigantic allies of Sweden* than do any 

 other American Leper ditia that I have seen. Still it is not 

 without good points of relationship with L. Canadensis; and, 

 for the present at least, I propose to term it L, Canadensis, var. 

 Anticostiana. 



In the series brought me by Mr. Billings there are several 

 specimens of Leperditia-rock from the Chazy limestone f of 

 L'Orignal, Canada. 



No. 3. Amongst these I recognize, in fragments from "near 

 the N.W. corner of the township of L'Orignal, C. W.,^^ the 

 Isochilina Ottawa, under similar conditions to those in which it 

 occurs at the Grenville Canal, except that in one specimen it is 

 associated with a ModiolopsisAWe, shell. I have only to remark, 

 that, when the shell is broken off, the casts of the valves show a 

 distinct muscle-spot (concave on the inner side of the valve) 

 with numerous radii. 



No. 4. Several specimens of a dark-grey limestone, labelled 

 " 1 mile west of L^Orignal," are rich in valves (separate) of a 

 handsome Leperditia, which, at first sight, has much the aspect of 

 Isochilina Ottawa ; but it is larger, blacker, has a proportionally 

 shorter hinge-line, the hinder portion of the valves being boldly 

 and obliquely rounded, forming about one-third the length of 

 the carapace ; and, though the valves have a marginal rim, this 

 is only on the two ends, being wanting below, where the middle 

 third of the ventral border is turned in, overlapping on the 

 right, and overlapped on the left side. The surface is smooth ; 

 the eye-spot prominent, and accompanied by a slight, irregular 

 nuchal furrow ; muscle-spot indistinct. The carapace is -^^ in. 

 long, 2^Q in. broad, and gn i"* thick, and most convex at the 

 anterior third. 



Though numerous in the rock, the individuals are not massed 

 together in layers, as the Isochilinm are at L'Orignal,| Grenville, 

 and White Horse Rapids. I propose to distinguish this well- 

 marked species by the name of Leperditia amygdalina. 



I take this early opportunity of correcting some important 



* Annals Nat. Hist. 2 ser. vol. xvii. p. 85. pi. 6. 



t This stratigraphical horizon is nearly coincident with that of the " two- 

 foot limestone" and Isochilina-bed described in the April No. of the 

 'Annak,' pp. 245 and 248, as being at or near the summit of the "Calr 

 ciferous Sandrock." 



