218 F. R. Couper Reed— Fossils from Dufton Shales. 
obsolescence of the accessory lobe, and in the division of the posterior 
lobe, but the division is not so complete in B. Chambersi, nor the 
posterior horn so long and pointed and recurved. ‘The complete 
division of the posterior lobe is more like that in the B. tuberculata 
group, but the lobes are connected ventrally. The posterior lobe is 
divided in B. (Cer.) quadrifida, Jones,’ and there is a somewhat 
similarly situated accessory lobe. 
Bryricuia (CreENoBOLBINA ?) SUPERCILIATA, sp. noy. Pl. XVII, 
Figs. 14, 14a. 
Carapace small, semi-elliptical, about twice as long as wide, with 
rounded sub-truncate ends, sub-rectangular cardinal angles and hinge- 
line somewhat shorter than maximum length of carapace ; anterior and 
posterior ends of sub-equal size. Valves rather convex, crossed by 
three lobes of unequal size and development, with a fourth smaller 
accessory one on inner side of posterior lobe; all lobes united below 
and merging into rounded sub-marginal ridge. Anterior, posterior, and 
ventral margins thick, with narrow flange projecting above the 
border and bearing a row of delicate radiating short straight 
spines set at equal distances apart ; border thickened, inclined at right ~ 
angles to plane of valves and widening somewhat posteriorly. Anterior 
lobe on valves broad, somewhat swollen, rounded, in width equal to 
about one-third the length of the valve; first sulcus nearly vertical, 
at right angles to cardinal edge and extending about one-half to two- 
thirds of the distance across valve; second lobe narrower than anterior 
one, sub-median in position, more prominent near dorsal edge, slightly 
curved back ventrally ; second sulcus sub-parallel to first, of sub-equal 
length, a little wider dorsally and slightly curved back ventrally 
below accessory lobe; posterior lobe as large (or nearly so) as anterior 
one, with small accessory tubercular lobe about half-way up its inner 
slope, elongated and nearly vertical and almost circumscribed by 
furrows; accessory furrow short, connected above with second sulcus. 
Surface of valves minutely granulated, and dotted with a few small 
scattered tubercles which are especially numerous and have a roughly 
concentric arrangement near ventral margin; a specially large tubercle 
is situated close to the cardinal edge on each of the three main lobes 
and usually two near the ventral margin; three smaller ones are 
usually present in a vertical line on the middle lobe. 
mm. 
Dimensions. Length ve - about 2°25 
Width a - about 1°50 
Remarks.—This species closely agrees with B. cvliata, Emmons,” but 
the presence of the small accessory lobe, the narrower posterior lobe, 
and the situation of the spines on the flange instead of along the edge 
of the valves sufficiently distinguish it. In the B. ( Cz.) subcrassa 
section of the genus or sub-genus Céenobolbina there sometimes exists, 
according to Ulrich,’ a similar small accessory lobe. 
1 Jones, Contrib. Micro. Paleont. Canada, 1891, pt. iii, p. 66, pl. xi, figs. 194, d. 
2 Jones, Q.J.G.S., 1890, vol. xlvi, p. 19, ‘Dl. ii, figs. 12-15; pl. iv, figs. 16-18. 
: Ulrich, Proc. U.S. Nat. Mus. a 1908, vol, XXxv, p. 309. 
