some British Fossil Crmstacea. 413 



cies flat ; surface marked with fine, imbricated striae, obliquely 

 longitudinal. 



In their pod-like form some of the species resemble such shells 

 as Solenocurtus and Solenimj/a, except in the abrupt truncation 

 of the posterior end ; others resemble the Crustacean genus 

 DithyrocariSf 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 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 Cytliere 

 or Cypridiniay and the two ocular spots separate them from all 

 others. T 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 diff'erence in their minerali- 

 zation ; 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 

 structui'e, with the double-eyed Cypridinia 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 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 ^nterior margin ; from the 

 internal (dorsal) anterior angles a small furrow extends a little 

 way obliquely backwards and outwards ; oblique longitudinal 

 strise 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 Solen 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, 



