550 PliOF. T. K. JONES ON SOME DEVONIAN AND 



XIII. PoLYcoPE, Sars, 1865. 



22. POLTCOPE SFBLENTTCULAEIS, Sp. IIOV. (PI. XXI. figS. 6 CI, ()h.) 



Length 1*1 mm. ; height -86 mm. ; thickness -53 mm. 



This suborbicular form reminds iis of Foli/cope, being round and 

 only slightly angular on its dorsal border. Whether one side or 

 the other of the low dorsal angle corresponds to a hinge-line, or if 

 the hinge were limited to the umbo-like angle itself, is uncertain. 

 Among the Devonian forms, however, of this genus, Polt/coj^e 

 Hiu/Jisice, Whidborne, and P. devonica, Jones, var. concinna, Whid- 

 borne, show a decided tendency to have a subangular dorsal border. 

 See ' Monogr. Devonian Pauna,' Pal. Soc. 1889, pp. 49, 50, pi. iv. 

 figs. 11 « & 17 «. 



Among Silurian Ostracoda, Macrocypris "^ crasstda., Jones, 'Ann. 

 & Mag. Xat. Hist.' March 1887, p. 181, pi. vii. fig. 10, is one of 

 the nearest, but it is too nearl}^ reniform, and has not such a uni- 

 form convexity. Primitia (Aparchites) Maccoyii, junior, Salter, sp. 

 (J. & H., ' Ann. & Mag. Xat. Hist.' ser. 4, vol. ii. p. 55, pi. vii. fig. 3), 

 is still nearer in shape, but is too uniformly oval in outline. 



Several of these round valves, usually black in colour, accompany 

 Bairdia anficosfiensis, Bytliocypris ohtusa, &c., on the bed-planes of 

 the thin grey limestone at English Head, Anticosti. Coll. Dr. Gr. J. 

 Hinde, P.G.S. 



§ II. From Dundas, Ontario, Canada. (Species, nos. 23, 24 ; p. 545.) 



Among the Upper- Silurian Ostracoda collected by Dr. Hinde in 

 North America, and noted in the February Xo. of the ' Quart. Journ. 

 Geol. Soc' p. 28, are numerous small and rather obscure forms in a 

 thin, brownish, earthy shale (with impressions of Ortliis, &c.) from 

 the Niagara Formation at Dundas, Ontario, Canada. Most of these 

 little Entomostraea are Primitice (1 mm. long, and less), neatly 

 suboblong in outline, with a mid-dorsal sulcus and a marginal rim. 

 The sulcus has its edges partially thickened in some specimens. 

 These features belong to P. mundida. In a few individuals a verj' 

 small, but distinct, tubercle appears in the sulcus or on one of its 

 edges, giving the appearance of a minute (or young) Beyrk-hia 

 notata, or a B. Kloedeni, var. acadica (compare some of the figs, in 

 pis. xvi. & xvii., ' Ann. & Mag. Xat. Hist.' May 1889). There is 

 also at least one small B. KJcedeni (more than 1 mm. long), with its 

 three well-developed lobes. These are not figured here. 



§ III. Silurian Ostracoda from the Dominion of Canada, CoV. Geol. 

 Survey of Canada. (Species, nos. 25-35; p. 545.) 



A. From Mr. H. M. Ami, F.G.S. Lower Silurian ; Canada. 



§ r. Utica Shales. 



1. Frimitia mundula, Jones. 



2. Ulruhi, Jones. 



§ II. Chazy Limestone. 



1. IsochUina Ottawa, Jones, variety. 



