76 On Ancient Water-jieas of the 



Part III. — PoLYCOPiDiE, Cytherellid^, M. Bakrande's new 

 Genera, and Entomidid^, 



The recent genus Polycope has no notch, though sometimes 

 there is a slight indication of its place. So in some fossil valves we 

 have either little indication, or none at all, of the Cypridinal notch. 

 These I group under the generic name of Polyoope, with the same 

 proviso and reservation as I adopt in using " Cypridina " for some 

 of the notched forms. Polyeope is represented by three species in 

 the Lower Carboniferous rocks of Settle, Carluke, Cork, and Meath. 



Cytherella has strong, thick, oval, or oblong valves, one fitting 

 at its edge into the other, and has existed from the Carboniferous 

 Period to the present day. C. hrevis * is one of the few species of 

 that genus yielded by the Lower Carboniferous strata. 



Cijtherellina is of Silurian age and obscure in character ; thick- 

 ness of shell and internal impressions remind us of the foregoing 

 genus. G. siliqua \ is the only known species. 



jEchminaX is also Silurian, both British and American, and 

 obscure in its relationship. 



M. Barrande's Nothozoe (from the Silurian of Bohemia §) has 

 simple oval valves, with thickened ventral margin; his Callizoe 

 (from the same) is narrower, indented antero-ventrally, and has a 

 group of tubercles in that region. Aristozoe, Barrande, not un- 

 common in several forms in the Silurian of Bohemia, sometimes (as 

 in A. prselonga) approaches our Carboniferous BJiomhina in shape, 

 but has a group of low tubercles in the antero-dorsal region, and a 

 faint nuchal furrow behind them, as in some Leperditise, but more 

 strongly marked. Orozoe, Barrande, also from the Silurian of 

 Bohemia, is similar in general features, but has two large tubercles 

 in the dorsal region, with the furrow between them, as occurs in 

 some small Primitise. Altogether, these sometimes large Bohemian 

 Ostracods, though not destitute of signs of alliance, differ largely 

 from Leperditise on the one hand, and Cypridinm on the other. 



Quite different from the foregoing genera, and evidently be- 

 longing to a separate family, in which the organs of locomotion did 

 not require anterior gape, notch, or hood, are the Entomididse, 

 comprising (1) Entomis, in which the dorsal or nuchal furrow is 

 very strong, but reaches only half-way across the valve, with or 

 without a tubercle on one of its margins ; and (2) Entomidella, 

 in which this sulcus crosses the valve obliquely, dividing off the 

 anterior third as a separate region ;|| recognized as Entomidella 

 in 'Annals Nat. Hist,,' June, 1873, p. 416. Entomis coneentrica 



* Plate LXL, Fig. 4, vol. iv. f Plate LXI., Fig. 5. 



J A. aiid E. cuspidata, Plate LXI., Fig. 6. 

 § ' Sil. Syst. Bolieme,' vol. i., suppl. 1872. 

 II See Plate LXI., Fig. 12, termed Entomis divisa at p. 185, vol. iv. 



