THE TERTIARY FORMATION. 17 



Carapace large, oblong, almost cylindrical, smooth, shining, beset with scattered 

 setae (of a greenish colour, with variations of tint in patches, and hairy at the margins, 

 in the recent state) ; anterior portion compressed, obhquely rounded, and tapering 

 forwards and downwards ; posterior rather less compressed than the anterior extremity, 

 almost squared, but with the angles well rounded ; dorsal margin straight along the 

 middle, suddenly rounded posteriorly, and gently curving anteriorly towards the antero- 

 ventral margin ; ventral margin slightly incurved. 



Hingement simple. Lucid spots large, elongate, 6 — 8, arranged in four irregular, 

 parallel, obhque rows (System a) ; in the outside pairs the spots coalescing one with 

 another. 



Dorsal profile lanceolate ; end view broadly and acutely ovate. 



Fig. 7 a represents a variety, from Clacton, which was much more setiferous (as 

 evidenced by the remaining pedicles of setae), and usually of smaller size, and marked 

 with proportionally larger lucid spots. I have met with this variety in a recent state 

 in beach-sand from Pegwell Bay, with which my friend Mr. Pickering has favoured 

 me, where it was associated with Candona lucens and Cytherideis trigonalis ; but of the 

 exact habitat of these specimens I have no precise information.^ 



Candona rejjtans is referred by Liljeborg to his section of Cyprides with very short 

 setae on the pediform antennge. I cannot find on our specimens even the six setse 

 mentioned by this author. The one large and three small setse at the third joint of 

 the second pair of antennae poorly represent the filamentous brush of the Cypris. The 

 character of the second pair of maxillse, referred to by Liljeborg, is an important 

 peculiarity ; possibly the two animals are distinct. I prefer following Baird in the 

 allocation of the species under notice, which is characteristically a Candona in its make 

 and habits. 



Candona rejdans is one of the largest of the bivalve Entomostracans met with in our 

 fresh waters, and is of frequent occurrence. It is plentiful in a fossil state in the 

 peat-deposits of Berkshire, at Newbury, and in the fresh-water marl in the fens of 

 Cambridgeshire, described by Mr. Hamilton \ it occurred also in the fresh-water 

 deposit met with in the Casewick railway-cutting, in Lincolnshire, and described by 

 Mr. Morris, ' Quart. Journ. Geol. Soc.,' ix, p. 321, and at Edwardstone ;^ and it is not 

 rare in the pleistocene sands and clays of Clacton and Grays, in Essex. The speci- 

 mens from Clacton, as already mentioned, are comparatively small ; those from Grays 

 are often very large. 



1 They were probably brought down by the river Stour. 

 ^ lioc. cit. 



3 About thirteen miles from Stanway, Essex. Mr. J. Brown kindly communicated some fine specimens 

 obtained from the post-tertiary deposits at this place. 



