Palaozoic Bivalved Entomostraca. 341 



coinparativfly large uiul well-grown specimens as belonging to 

 another speeific type. This Trenton form, which I ])ropose to 

 term L. ('unailcnsis, var. Jusepliiana, may possibly be the same 

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



The neatly shaped Leperditia from Anticosti more nearly 

 resembles its almost gigantic allies of Sweden* than do any 

 other American Lepcrditue 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 scries brought me by Mr. Billings there are several 

 specimens of Leperditia-roek from the Chazy limestone f of 

 L'Orignal, Canada. 



No. 3. Amongst these I recognize, in fragments fi'om "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 Modiolopsis-\\ke shell. I have only to remark, 

 that, when the shell is broken ofiF, 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 caraj)ace ; 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, in-egular 

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

 long, -^-^ in. broad, and 2% ^^- thick, and most convex at the 

 anterior third. 



Though numerous in the rock, the individuals are not massed 

 together in layers, as the Isochilince 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 stratifrrapliical horizon is nearly coincident with that of the " two- 

 foot limestone " anil Isochilina-bcd described in the \\)v\\ No. of the 

 ' Annals,' pp. 245 and 248, as being at or near the summit of the " Cal- 

 ciferous Sandrock." 



