BRITISH FOSSILS. 



PLATE I. FIGS. 13-15 (AND 16, VARIETY) ; 

 PLATE XV. FIG. 2. 



P. PEKOBNATUS. 



P. pedalis et ultra, undique squamulis minutis ornatus, capite semi-ovali, 

 fhorace segmentis latis curvatis, oculis anticis minoribus granulatis. 



SYNONYM. H. perornafus. SALTEK, in Quart. Geol. Journal, vol. xii. 

 p. 31, and 28, fig. 6. 



One of the most distinct and well-marked species, and clearly 

 belonging to the same section with H. bilobus, while it is more than 

 double its length and width, the largest specimen being three inches 

 and a half wide and probably not less than fifteen inches in 

 length. We have the head and six body segments ; the swimming 

 feet, both attached and free ; maxillse with palpi, the post-oral plate 

 in situ, with some faint traces of antennae ; but all these show good 

 characters. 



The head (carapace*) was formerly described by me as smooth, but 

 in better specimens it is closely and fully sculptured, the plicas convex 

 forwards. It is half a broad oval (fig. 13), three inches in length 

 by three inches in breadth, and the posterior angles are acute. 



The eyes are forward and rather small, not extending over a 

 space more than two-fifths the length of the head (in H. bilobus 

 they are much more than half), and finely granulated, the lenses 

 visible to the naked eye (fig. 13). 



The body segments are broader from front to back than in the 

 last species, the front ones particularly, but, if fig. 16 be the same 

 species, vary considerably in this respect. They are much arched 

 forwards over the wide central portion, the ends are recurved as 

 usual, and at less than one-third from the middle (6) a kind of fulcrum 

 exists, dividing the compressed lateral area (pleura) from the more 



* I take leave to use in description the term " head " for convenience' sake ; carapace 

 is of course more correct. 



