the Palaozoic Bivahed Entomostraca. 423 



Professor Dr. Ferdinand Roemer, of Breslau, who has already 

 enlarged our knowledge of palaeozoic fossils from the Scandina- 

 vian Limestones. 



21. Primitia obsoleta, nov. PI. XIII. figs. 12 a, b,c. 



Length -^Vo (iro)j height -^, thickness -^ inch. 



Carapace-valves obtusely subovate, straight at the back, con- 

 vex ventrally; one end broadly and obliquely curved, with a 

 dorsal angle, the other semicircular; a slightly raised smooth 

 rim runs along the ventral border, continues along the broad 

 end, widens at the dorsal angle, and dies out on the hinge-line. 

 Surface convex, slightly flattened towards the narrower end, 

 smooth, and presenting, at the middle of the dorsal region, a 

 faintly indicated impression, fainter even than the shallow sulcus 

 in its companion P. Beyrichiana. 



In Scandinavian limestone (Upper Silurian), drifted blocks, 

 North Germany. 



22. Primitia ohlonga, nov. PI. XIII. figs. 14 a, Z>,c. 



Length -^, height -ttV^ thickness -^ inch (3j : 2 : 1). 



Carapace-valves convex, sloping gently and nearly equally to- 

 wards the margins, oblong, with rounded, almost symmetrical 

 ends; the dorsal line slightly sinuous, and the ventral line very 

 faintly convex. Surface smooth. The slight sinuosity of the 

 dorsal line is probably a trace of the sulcus, as in P. radiata and 

 other associated forms. The ventral margin is very slightly 

 thickened by being suddenly inturned. Excepting this last 

 feature, the absence of positive characters in this relatively large 

 form might have made us doubtful whether it be really a Pri- 

 mitia as defined above, or whether we ought to have classed it 

 as a Cythere, with some fossil and recent carapaces of which it 

 might almost equally well be compared. 



In the Scandinavian limestone blocks (Upper Silurian) from 

 Northern Germany. 



23. Primitia ovaia^ nov. PI. XIII. figs. 13 a, b, c. 



Length -^^, height ^, thickness ~^\ inch. 



Carapace- valves nearly ovate, excepting that the dorsal margin 

 is not so convex as the ventral ; extremities round, but one much 

 narrower than the other; surface smooth, convex, sloping off 

 gently towards the ends ; ventral border thickened by a sudden 

 inturn of its edge, with a low rounded ridge at the angle of 

 deflection. In this last feature it has an alliance with P. obso- 

 leta ; but its outline, want of postero-dorsal angle, and smaller 

 convexity distinguish it. 



Drifted Scandinavian limestone (Upper Silurian), with P. ob- 

 soleta, &c. 



