246 Mr. T. R. Jones on North American 



Mill, on the Castor River (Russell Township), are three glossy 

 black valves, in good preservation, and of different sizes (one 

 specimen being y% in. long and f^ broad; the others being 

 respectively -^^ in. and -£^ in. in length). In each of these 

 the eye-spot is very distinct, and accompanied by a local rugged- 

 ness of the surface of the valve (not amounting to a sulcus), and 

 the valves are faintly rimmed. 



This black limestone is referred to the " Trenton" in ' Geol. 

 Surv. Canada Report,^ 1851-52, p. 73 ; but, according to a letter 

 of later date from Sir W. E. Logan, it may be " Birdseye lime- 

 stone/' 



A small specimen of brownish, fiue-grained limestone (wea- 

 thering grey, and containing shells), from Pauquette's Rapids, 

 Allumette Island, Ottawa River, contains one well-preserved 

 brown-coloured valve (fig. 17), J mch long, -^^ inch broad, 

 much like the largest specimen from Louck^s Mill, but showing 

 no marginal rim, and feeble traces only of the eye-spot and its ac- 

 companying depression. In this fragment of (probably Trenton) 

 limestone smaller Entoraostracous bivalves abound (see p. 249). 



Excepting in the relative size, the form of the eye-spot, and 

 the valve-margin (in which latter points one of these larger spe- 

 cimens varies from the others), the two sets of specimens (the 

 large and the small) do not appear to disagree essentially, as far 

 as my means of examination at present enable me to judge. At 

 the same time, as we know that, in some recent bivalved Ento- 

 mostraca, different species and eA^en subgenera may present a 

 great similarity in their carapaces, it is possible that we have 

 here a separate specific form. 



Mr. Conrad has briefly described*, under the name of " Cy- 

 therina fahulites,'' a bivalved Entomostracan, from the Trenton 

 limestone of Mineral Point, Wisconsin. This appears to be a 

 Leperditia half an inch in length, and therefore surpassing in 

 size the specimens under notice, to which it may be allied. 



Other localities in Canada are mentioned by Sir W. E. Logan 

 and Mr. oMurray for Entomostraca — probably L. Canadensis or 

 allied forms : namely : — 



Three miles above Lachine; in the Trenton limestone?t. 



Indian Lorette near Quebec; in the Birdseye limestone ? J. 



" Three or four miles from INIontreal city, in a line a little 

 west of north; in Birdseye limestone §." 



* Proceed. Philad. Acad. vol. i. p. 332. 



t Quart. Journ. Geol. Soc. vol. viii. p. 205. 



X Letter, Jan. 17, 1853. § Letter. 



