100 BRITISH FOSSILS. 



linear portion, and terminating in a slight prominence. The whole 

 piece is smooth. 



Of the first body ring a fragment an inch and a half long and 

 one inch wide is figured (Plate X. fig. 2). It is the semi-circular 

 sweep of the outer edge of the segment, where it fits into the 

 scooped out portion of the succeeding (second) one. The rounded 

 margin a is serrated, the serrations pointing backward. The 

 sculpture is very minute, prominent, and confined to the forward 

 half, except a few marginal plica3 on the hinder edge. All are longer 

 than wide. Fig. 2a shows them magnified. Fig. 3 is without much 

 doubt the second thoracic segment. It is wider at the sides than in 

 the middle, and turns up abruptly at the forward angle to form the 

 characteristic process. Fig. 4 appears to be a larger specimen of 

 the third ring, it has the same characters of ornamentation. In 

 both the central portion is less arched than in P. anglicus or 

 P. arcuatus, and the sides less oblique and minutely crenulate. 

 A narrow (articular ?) furrow runs along the middle portion of the 

 anterior edge, followed by a convex ridge, which is bounded by a 

 row of prominent minute tubercles extending a good way out, and 

 nearly to the lateral margins. Behind this the anterior third of 

 the segment is occupied by the sculpture, which is much more pro- 

 minent and tubercular, and less scale-like than in the large Scotch 

 species. 



The occurrence of this line of tubercles enables us to connect with 

 the species some very curious fragments, one of which is here 

 figured (fig. 8) with one or other of the body rings. When first 

 viewed the piece appears quite anomalous, the extended ends giving 

 the general form much the aspect of the epistoma, but a closer 

 examination shows that it has an upper surface b, and the impres- 

 sion of the lower side c, each with the sculpture pointing backwards, 

 and with no room for a median lobe. Of the epistoma we have 

 now obtained specimens (fig. 1, as above described), and it remains 

 therefore to explain this piece as one of the body rings, obliquely 

 pressed, (probably the exuviated crust only,) the angular edge being 

 indicated at a, and one surface (the inferior) c, being less disturbed 

 and altered in shape than the other, b. The dotted lines will give a 

 notion of what was probably the complete form. Fig. 9 is probably 

 a similar fragment. Figs. 10 and 11 have as yet no explanation. 

 Fig. 7 shows the true outline of another ring, which has been com- 

 pressed vertically in the rock, instead of laterally. These specimens 

 of course give the true idea of the convexity, which was very great. 

 The form was almost cylindrical. 



