50 BRITISH FOSSILS. 



face is covered with semicircular plicae, the curves of which open 

 backwards (contrary to the usual position over the rest of the body). 



In front is seen the impression of the large ovate median lobe (a) 

 of the epistoma, shaped as usual, and behind are two radiated mus- 

 cular impressions (6) placed low down on the carapace, and towards 

 the median line, which impressions are probably the attachments 

 of the great swimming feet. 



We have only space to figure one of the seven body segments : 

 the anterior six are probably thoracic, the last of these having a 

 large projecting hinder angle which overlaps the base of the seventh 

 (or first abdominal) segment. All the segments are conspicuously 

 broader in proportion than in H. perornatus, the second, third, fourth 

 fifth, instead of nearly five times as wide as long, being not above 

 three and a half times, and this difference is remarkable in the front 

 segment (c), which in H. perornatus is very transverse, seven times as 

 broad as long, but in this is only four times and three-quarters as wide. 

 It has very distinct anterior lobes, like those of the second segment. 



The sculpture of the rings differs from that of P. perornatus in 

 having the plicae narrower and longer, the angular ones being less 

 than 90, and even on the anterior margin they are not less than 

 semicircular. 



Each segment except the first is crossed by a very distinct 

 impressed line, which bisects the anterior sculptured half, and is placed 

 in the second segment at the anterior third (in the first segment it 

 is absent), the rest have it very near the anterior margin. 



The seventh segment is two and a half times as broad as long, 

 and has square, not produced posterior angles. 



Locality. Lesmahago. Mus. Pract. Geology. (Collected by Mr. 

 R Slimon.) 



