348 Prof. T. R. Jones on 
Schmidt regards it as a Leperditia, | think that the former is 
correct. Among Schmidt’s figures of one cast and three valves 
there are sufficient variations to cover any slight differences that 
the one specimen from North America may exhibit, as com- 
pared with any one of those figures of the large Upper- 
Silurian form from Scandinavia. 
PriMITIA, Jones & Holl. 
Primitia, Jones & Holl, 1865, Ann. & Mag. Nat. Hist. ser. 3, vol. xvi. 
p- 415, and 1868, ser. 4, vol. ii. p. 55 &c.; Jones, Pal. Biv. Entom. 
Proceed. Geol. Assoc. 1869, p. 8 &c.; Barrande, 1872, Syst. Sil. 
Bohéme, vol. i. suppl. p. 539. 
1. Primitia simplex, Jones, varr. 
Pl. XX. figs. 1, 2, 3. These are simple Primitie, common 
in some pieces of limestone from the “ Saint-John group” of 
St. John’s, in Newfoundland, given to me in 1866 by the late 
Mr. T. G. B. Lloyd. This rock is referred to the “‘ Lower 
Potsdam” (‘Cambrian’) by Prof. John Milne, F.G.8., in 
the Quart. Journ. Geol. Soc. vol. xxx. p. 743. 
Figs. 1, a, 6, are the outlines of a right valve, about 4 ich 
long; figs. 2, a-c, of a complete carapace 34; inch long; and 
fig. 3 isa drawing of aright valve, about 2 inch long. These 
valves differ but slightly among themselves in their shape, 
having a nearly semicircular ventral curve, with a broadly 
ovate outline of body and straight back. Figs. 1 and 2 have 
a relatively high convexity. Fig. 3 shows the most symme- 
trical ends ; fig. 1 has the postero-dorsal slope more expressed 5 
and fig. 2 has the hinge-line extended so far back that this 
slope is almost lost. Fig. 1 is like the Lower-Silurian Pri- 
mitia simplex, Jones (Ann. & Mag. Nat Hist. ser. 2, 1855, 
vol. xvi. p. 173, pl. vi. fig. 255; and ser. 3, vol. xvi. p. 417), 
of Portugal and Shropshire ; but it shows no trace of a dorsal 
notch or furrow. Fig. 2 is also somewhat like P. simplex, 
and is even more comparable with P. obsoleta, Jones & Holl 
(Ann. & Mag. Nat. Hist. ser. 3, vol. xvi. p. 423, pl. xiii. 
fic. 12), from the Upper Silurian of Scandinavia; but it is 
more convex than the latter, and has not its marginal rim. 
Fig. 3 represents P. s¢mplex in a general way ; but, instead of 
a simple dorsal notch it has aslight curved, subspiral, comma- 
shaped elevation, due to a narrow semicircular depression on 
the convexity of the valve, and a small curved, tapering, con- 
centric furrow within the other on the dorsal region. 
Fig. 1. P. simplex, var. Sanctojohannesiana. 
Fig. 2. —— ——, var. Lloydiana. 
Fig. 3. —— ——., var. Milneana. 
