304 



Gexis rEIMITIOPSIS. Jones. 



[Ety. : Derived from Primitia.] 

 (1887: Notes ou some Silurian Ostracoda, from Gothland, p. 5.) 



Carapace bivalvecl, resembling Primitia externally. excejDt 

 that the anterior end has a specially smooth area cor- 

 responding- to an intei'nal portion, which is partitioned off 

 from the rest of the cavity by a cross-wall. 



Primitiopsis PixcTULiFERA. (Hall.) (Fig. 243.) (Leper- 

 ditia punctulifera. Hall: 13th Ann. Rep't N. Y. State Mns. 

 Nat. Hist., p. 92.) 



Distinguishing Oia7-ar^ei>.— Snb-cylindrical ontline: sub- 



eqnal ronnded extremi- 



ties ; snrface with three 

 snmll smooth tnbercles, 

 and a reticulated mesh- 

 work, which gives the 

 appearance of minute 

 pits, and dies out at the 

 ends ; meshes more dis- 

 tinct around central tu- 



era. A yoimg i ^ i 

 left valve : lateral and edge views of a left valve, DCrCie. 

 X 25 (after Jones). -n i i • 



Jb ound commonly ni 

 the Lower shales, at Sections 5 to 8 ; and on the Lake 

 Shore. 



Gexus EXTOMIS. Jones. 



[Ety. : Entoma, cut in two.] 

 (1873: Ann. and Mag. Nat. Hist., Ser. IV., Vol. XI., p. 413.) 



Carapace ovato-oblong, bean shaped, rounded at both 

 ends. Valves equal, indented by a vertical sulcus. Avhich 

 begins at about one-third the length of the valve from the 

 front, and extends about half way at-ross the valve. There 

 is often a spine or tubercle in front of the furrow. 



Entomis rhomboidea. Jones. (Fig. 244.) (Quart. 

 Journ. Geol. Soc, Vol. XLYL, p. 10, 1890.) 



