406 Prof. T. R. Jones on the 



cit. pi. xiv. fig. 8). Tlie ventral margin of P. grandis has a 

 delicate piinctation, due apparently to the meshes of the 

 ornamental network coming against the raised marginal rim. 

 From Frojel. 



5. Primitia reticristaia^ Jones. 

 (PI. XXII. figs. 15 a, 15 &, 15 c.) 



Primitia reticristata, Joues, Silur. Ostrac. Gothland, 1887, p. 5. 



This is closely allied to P. cristata, J. & H. (Ann. & Mag. 

 Nat. Hist. ser. 3, vol. xvi. 1865, p. 420, pi. xiii. fig. 1). It 

 differs, however, somewhat in outline, being more semicircular 

 in its contour, and especially in having a beautifully reticulate 

 surface. 



About twelve specimens were among those sent in 1886. 



From Frojel. 



6. Primitia seminulum^ Jones. 

 (PI. XXII. figs. 17 a, 17 h.) 



Primitia seminulum, Jones, Silur. Ostrac. Gothland, 1887, p. 5. 



This is a variety of P. seminulum^ J. (Ann. & Mag. Nat. 

 Hist. ser. 5, vol. xvii. p. 413 for references, pi. xiv. fig. 14). 

 It is slightly modified, being rather longer than the British 

 specimens. Three or four among the specimens sent in 1886. 



From Frojel. 



IX. Peimitiopsis, Jones, 1887. 



Primitiopsis, Jones, Silur. Ostrac. Gothland, 1887, p. 5. 



This is like Primitia externally, except that the anterior 

 end has a specially smooth area, corresponding with an 

 internal portion, which is partitioned oflf from the rest of the 

 cavity by a cross wall. 



1. Primitiopsis planifrons, Jones. 

 (PI. XXII. figs. 18 a, 18 Z*, 18 c, 18 J.) 



Primitiopsis planifrons, Jones, op, cit. p. 6, woodcuts. 



Suboblong, with rounded ends ; bearing a faint sulcus, to- 

 gether with the subcentral pit, which is normal in Primitia ; 

 also another slight furrow is observable in the anterior dorsal 

 region. The convexity is greatest along the ventral region, 

 as is usually the case with Primitice of the group to which 



