FE. R. Cowper Reed—Fossils from Dufton Shales. 219 
Bryrrcura (T'errapetta) TurRNBULLI, sp. nov. Pl. XVII, 
Figs. 12, 12a, 13, 13a. 
Carapace obliquely semi-elliptical, somewhat elongated with hinge- 
line as long as carapace and anterior end somewhat narrower than 
posterior, which is broadly rounded. Valves moderately convex, 
divided by three unequal sulci into four lobes, all connected ventrally 
with rounded sub-marginal ridge. Anterior lobe largest, more or less 
swollen and pear-shaped, in width equal to quite one-third the length 
of carapace, narrowing ventrally; first suleus longest and widest, 
slightly oblique or curved back below, but starting at right angles to 
cardinal line, extending about two-thirds to three-fourths across the 
valve; middle lobe almost median, narrow, rounded, about one-half 
the width of anterior lobe, at right angles to cardinal edge; second 
suleus sub-parallel to first, slightly oblique, of same strength as first ; 
accessory lobe smallest of all, more or less nodular, not reaching 
cardinal edge, situated on inner side of posterior lobe, and connected 
by depressed narrow neck with sub-marginal ridge ; accessory furrow 
short, weaker than others; posterior lobe rounded, about two-thirds 
the width of anterior lobe or nearly as large. Border of valves with 
horizontally extended rounded convex flange, separated off by deep 
marginal furrow; flange very narrow in front, widening posteriorly, 
crossed by regularly placed faint radial grooves, with fine stric 
on edge, making a minutely fimbriated and denticulated margin. 
Anterior end of valves provided with a few small marginal spines set 
along the edge of border below the flange. Surface of valves 
minutely granulated, with an irregular concentric row of small sub- 
equal tubercles close inside marginal furrow, becoming a double 
row below anterior lobe and at front end; a few larger tubercles 
irregularly distributed on the lobes. 
mm. 
Dimensions. Length  . : : - about 3-00 
Width (across middle) . . about 1°25 
Remarks.— We may compare this species with B. (Zetr.) marchica, 
Krause,’ and B. subguadrans, Ulrich,’ but the lobation, character of 
the flange, and ornamentation of our species do not completely agree 
with either. In B. complicata, Salter,*? the valves are shorter and 
wider, and the lobes are not developed relatively in the same manner ; 
the surface also is smooth (except in the variety decorata), and the 
flange and ornamentation are distinct in character. 
EXPLANATION OF PLATE XVII. 
Fie. 1. Acidaspis semievoluta, sp.nov. Head-shield without free-cheeks. x 4. 
Ditton Giibos ssc Oe 
>, 3 Ditto. Imperfect pygidium. x 4. 
5, 4. Homalonotus ascriptus, sp. nov. Head-shield without free-cheeks. x 25. 
», 4a. Ornamentation of ditto. x 12. 
»» 9. Ditto. Ornamentation of head-shield near anterior lateral angles of 
glabella. x 12. 
>, 6. Ditto. Head-shield of young individual (?) without free-cheeks. x 24. 
i Krause, Zeits. deutsch. geol. Ges., 1889, xli, p. 19, t. ii, figs. 9-11. 
> Ulrich, op. cit., p. 306, pl. xxxix, figs. 1-3. 
* Jones, Ann. Mag. Nat. Hist., 1855, ser. 1, vol. xvi, p- 163, pl. vi, figs. 1-5. 
