180 Proceedings of the Royal Physical Society. 



overlap. The limbs, of which each segment bears only on-e 

 pair, are on the anterior segments longer than the breadth of 

 the segment to which they are attached, and are made up of 

 seven joints. The coxae in their flattened state are about 

 1 mm. broad, the legs then expand towards the distal end of 

 the third joint, whence they taper to a point. The third 

 joint is much the longest, the others are sub-equal in length, 

 and the leg is terminated by a single claw. Where not 

 crushed, the legs are nearly circular in cross section, and there 

 is no appearance of spines at the articulations. The head, 

 which appears to be composed of several coalesced segments 

 from its being divided into several areas by deep sulci, is, when 

 seen from above, roughly triangular in shape, with the sides 

 slightly bulging. The anterior part is occupied by a penta- 

 gonal area, which is deeply pitted with numerous circular 

 depressions of the test. Lapping round three sides of the 

 above is a narrow area which bears near each of its anterior 

 extremities the pits into which the basal joints of the antennae 

 are articulated, the inner margin of the pits being streng- 

 thened by crescent-shaped ridges. The back part of the head 

 is occupied by a narrow area which extends across from side 

 to side, forming as it were a nuchal plate. Through about 

 half of its length the anterior margin of this area abuts upon 

 the preceding one, triangular eye-spaces forming the bound- 

 aries of the remaining quarters on each side. The eye-spaces 

 thus placed at the postero-lateral margins of the head are 

 large and triangular in form, and depressed somewhat below 

 the general level of the head plates. They are protected 

 anteriorly by raised ridges of the test which pass inwards 

 from the lateral margins at angles of about 45°, and lose 

 themselves in the sulcus which divides the nuchal from the 

 antennal area. The eye itself is made up of numerous facets 

 which are arranged in oblique rows, the posterior end of each 

 row being inclined downwards and outwards, the facets being 

 so numerous and so close together that the eye simulates a 

 compound one. Both the eye and the protecting ridge in 

 all probability represent original segments. The antennae, of 

 which three joints on each side have been preserved in one 

 specimen (PI. II., fig. 1), appear to be constructed on the type 



