24 Prof. T. Rupert Jones — Canadian Ostracoda. 



thicker, the valve being more convex. A much more pyriform valve 

 of Pontocypris, with an acute posterior extremity, is Reuss's Bairdia 

 subfalcata, Sitzungsb. Akad. Wiss. Wien, vol. xviii. 1885, p. 253, 

 pi. ix. fig. 91 ; but it is much narrower than our Fig. 3, and its 

 ventral margin is much more incurved. 



One specimen in the loose block of Saint-Mary-River Beds. 



Cypris, Miiller, 1785. 

 4. Cypbis Dawsoni, sp. nov. PI. II. Figs. 4a, h, c. 



Length 1-32, height -64, thickness -56 mm. 



A neat suboblong valve, straight on the venti'al, elliptically curved 

 on the dorsal margin ; ends almost equal in their semicircular curve, 

 but the anterior rather smaller and more compressed than the 

 posterior ; both curving off from the dorsal and meeting the ventral 

 margin with a definite angle. Surface gently convex ; smooth ; 

 minutely dimpled with probably the I'emains of a punctation nearly 

 worn away or partially dissolved ; it is also marked centrally witl?. 

 an obscure dark muscle-spot. 



Named after Dr. G. M. Dawson, F.E.S., who collected this and 

 many other interesting specimens of Natural-history in his ex- 

 pedition along the 49th parallel. 



There are some few forms of the marine genera Xestoleberis and 

 Krithe that have an approach to this figure in shape ; but it is 

 among some freshwater genera that we find the nearest resemblances. 

 Ostracods of this form, with straight ventral and well-arched dorsal 

 margin, and nearly equal ends, are mostly found among the fresh- 

 water CyprididcB ; and of the published figures we may point to — 



1. Cypris incongruens, Eamdohr. Trans. Linn. Soc. vol. xxvi. 1868, p. 363, 



pi. xxiii. figs. 16-19. 



2. Scottia Broxvniana (Jones). Trans. R. Dublin Soc. ser. 2, vol. iv. 1889, p. 72, 



pi. ix. figs. 23, 24. 



3. Erpetocypris strigata (Miiller). Ibid. p. 85, pi. viii. figs. 14, 15. 



The first, however, differs from our Fig. 4 in the outline of both 

 extremities ; the second is by far too tumid, and has a too boldly 

 arched back ; and the third has the proportions of the ends reversed, 

 that is, it is somewhat higher in front than behind. 



This one specimen is in a piece of the loose block found at the 

 South Branch of the Milk River, but belonging to the Saint-Mary- 

 River Beds higher up the valley. 



Ilyocypris, Brady and Norman, 1889. 

 5. Ilyocypris oblonga, sp. nov. PI. II. Figs. 5a, 6, c. 

 Length 1-12, height '6, thickness '10 mm. 



Oblong, slightly sinuous on the dorsal and quite straight on the 

 ventral margin, gently curved at the ends, each of which meets the 

 dorsal edge with a curve, and the ventral with a blunt angle. The 

 anterior slightly smaller than the other end. Surface gently and 

 irregularly convex, sloping down to the edges ; obscurely dimpled 

 all over; marked with an obscure central muscle-spot in a faint 



