304 



Genus PRIMITIOPSIS. Jones. 



[Ety. : Derived from Primitia.] 

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



Carapace bivalved, resembling' Primitia externally, except 

 that tlie anterior end has a specially smooth area cor- 

 responding to an internal portion, which is partitioned off 

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



Primitiopsis punctulifera. (Hall.) (Fig. 243.) \Lej>rr- 

 ditia ymnrtulifern. Hall: 13th Ann. Rep't X. Y. State Mas. 

 Nat. Hist., p. 92.) 

 Distinguishing Characters. — Sub-cylindrical outline: snb- 



equal rounded extremi- 

 ties : surface with three 

 small smooth tubercles, 

 and a reticulated mesh- 

 work, which gives the 

 appea ranee of minute 

 pits, and dies out at the 

 ends ; meshes more dis- 

 tinct around central tu- 

 ieft vX? bercle. 



Found commonlv in 



* 



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

 Shore. 



Fig. 243. Primitiopsis punctulifera. 

 left valve ; lateral and edge views of a 

 x 25 (after Jones). 



Gems EXTOMIS. Jones. 



[Ety. : Entoma, cut in two.] 

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



Carapace ovato-oblong, bean shaped, rounded at both 

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

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

 front, and extends about half wav across the valve. There 

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



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

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



