some British Fossil Crustacea. 413 
cies flat ; surface marked with fine, imbricated striz, obliquely 
longitudinal. 
In their pod-like form some of the species resemble such shells 
as Solenocurtus and Solenimya, except in the abrupt truncation 
of the posterior end; others resemble the Crustacean genus 
Dithyrocaris, with which I think their affinity hes, 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 resemble 
what we find in Crustacea allied to Apus rather than in Mol- 
lusca ; the general pod-like form, large size, and posterior trun- 
cation separate them from any of the large species of Cythere 
or Cypridinia, and the two ocular spots separate them from all 
others. I suspect from some of the specimens that the two sides 
meet along the dorsal line at an angle of 45°, with probably little 
power of motion. The ocular spots even when flat may generally 
be recognized with care from the difference in their minerali- 
zation ; they are often dark-coloured as if retaining some of their 
pigment, and have a shghtly granular aspect, corresponding in 
fact very closely, both in position on the shell and in apparent 
structure, with the double-eyed Cypridinia of the Indian Ocean. 
In one species there is a short sulcus extending on each side 
from the medial lne 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 solenoides (M‘Coy). 
Sp. Char. Sides meeting along the back at an acute angle, each 
being nearly four times longer than wide, the ventral margin 
nearly straight and parallel with the dorsal line ; anterior end 
narrowed and truncate obliquely forwards and outwards from 
the dorsal line; posterior end scarcely narrowed, truncated 
obliquely backwards and outwards ; valves evenly convex, the 
edge slightly thickened ; ocular spot a little depressed, close to 
about the middle of the truncated anterior margin ; from the 
internal (dorsal) anterior angles a small furrow extends a little 
way obliquely backwards and outwards ; oblique longitudinal 
striz very close and fine ; eyes two-thirds of a line in diameter ; 
width of each side from dorsal to opposite margin 5} lines. 
This much resembles a little So/en in form. The ocular. spot 
is generally dark-coloured. 
Common in the Upper Ludlow rock of Benson Knot. 
(Col. University of Cambridge.) 
Ceratiocaris ellipticus (M‘Coy). 
Sp. Char, Each side longitudinally elliptical, evenly convex, 
