Crustacea. ] LOWER PALAXOZOIC ARTICULATA. 137 
gently convex, posterior end abruptly truncated obliquely; on each side near the anterior end, considerably 
below the hinge-line, is an ocular (!) spot, sometimes raised and distinct, in some species flat; surface 
marked with fine, obliquely longitudinal, imbricated strize. 
In the pod-like form some of the species resemble such shells as Solenocurtus and Solenimya, except 
in the truncation of the posterior end; others resemble the Crustacean genus Dithyrocaris, with which 
I think their affinity lies, though they differ in form, and want the peculiar ridges of that group. I 
conceive they were phyllopodous crustaceans allied to Lymnadia: the peculiar texture and kind of lineation 
of the surface resembles what we find in crustacea allied to Apus, Ge. rather than in Mollusea; the general 
pod-like form, large size, and posterior truncation, separate the typical forms from any of the large species 
of Cypridina, and the two ocular spots separate them from all others. I suspect, from some of the specimens, 
that the two sides met along the dorsal line at an angle of about 45°, with probably little power of motion. 
The ocular spots even when flat may generally be recognized with care from the difference in their mine- 
ralization; they are often dark-coloured, as if retaining some of their pigment, and have a slightly granular 
aspect, corresponding in fact very closely, both in position on the shell and in apparent structure, with the 
double-eyed Cypridinw of the Indian Ocean. In one species there is a short sulcus, extending on each 
side from the medial line behind the eye obliquely backwards and outwards, reminding us of the, perhaps, 
somewhat similar nuchal furrow of Apus. I only know the genus in the upper Silurian rocks. 
CERATIOCARIS ELLIPTICUS (A/*Coy). PI. 1. E. fig 8. 
Ref —M°Coy, Ann. Nat. Hist. 2nd Series, Vol. IV. p. 413. 
Sp. Ch.—Each side longitudinally elliptical, evenly convex, about twice and a half longer than wide ; 
greatest width of the side and curvature of the margin about one-third from the anterior end, which is 
elliptically pointed; posterior end obtusely rounded, the oblique truncation nearly effaced; ventral margin 
convex; ocular spot elevated like a small tubercle, twice its diameter from the dorsal line, and about one-fourth 
the length from the anterior end. I believe the strize of the surface have the direction usual in the genus, but 
they are very delicate. Length, one inch three lines, greatest width of the side six lines. 
The elliptical form, prominence of the eye-spot, and its distance from the anterior end, mark the 
species well. 
Position and Locality—Rare in the Upper Ludlow rock of Benson Knot, Kendal, Westmoreland. 
Explanation of Figures —P1\. 1. E. fig. 8. Natural size, from Benson Knot. 
CERATIOCARIS INORNATUS. PI. 1. E. fig. 4. 
Sp. Ch—Valves twice and half as long as wide, moderately convex along the middle, abruptly con- 
tracted to a small mucronate point in front; dorsal line straight till near the anterior point, to which it 
slightly inclines; ventral margin most convex about the anterior third, which is the deepest part of each 
valve, from thence nearly straight to the posterior end, which is slightly narrowed, and truncated obliquely 
from the dorsal margin, the lateral angle being nearly of 90°; surface with short irregular impressed 
‘crustacean’ strize, imperfectly parallel with the ventral margin; ocular spot large ; flattened, its own diameter 
from the dorsal line, and about three diameters from the anterior end. Length, one inch eleven lines, greatest 
depth eight lines. 
In a note of Mr Salter’s this was named Dithyrocaris inornatus, and I have accordingly used his specific 
name on the explanation of the plate ; on revision, however, he has cancelled this, and requested me to describe 
it as of the genus to which I referred it. What Mr Salter took for a longitudinal lateral ridge, as in 
Dithyrocaris, may be seen from other specimens to be an accidental crumpling. The ocular spot escaped 
his notice, but is very distinct. 
Position and Locality—Not very uncommon in Upper Ludlow rock, at Benson Knot, Kendal, West- 
moreland. 
Explanation of Figure—PI. 1. E. fig. 4. Natural size of one side, from Benson Knot. 
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