34.0 Proceedings of the Royal Physical Society. 



P. Anglicus, which is also different from the former in having 

 the sculpturing confined to its anterior half only. The 

 squames on P. Dicki become more acute as they approach 

 the posterior margin, and are more highly embossed on the 

 dorsal than on the ventral aspect, though on the latter they 

 are somewhat the larger. The fringe above alluded to is 

 composed of these embossed squames, only they are 

 enormously produced when compared with those on any 

 other part of the segment except on the dorsal keel (PI. 

 VIL, Yig, 16). The individual squames of the fringe are 

 smooth above, but beneath they bear numerous other 

 elongated small squames (PL VIL, Fig. la). From the 

 fringe the test is rapidly inverted, and passes obliquely 

 inwards and forwards, forming a hollow inverted cone which 

 is abruptly truncated. This conical flange is also highly 

 ornamented with a particular acutely lobed, small, squamiform 

 pattern, the convexities of the scales pointing backwards, 

 clearly showing that this is not an accidentally folded-in 

 portion of the external test. The ornament ceases at a 

 distance of from half to three-quarters of an inch, when the 

 flange becomes smooth so as to form the posterior articular 

 surface, and the truncated edge ends in a corrugated skin- 

 like membrane, portions of which have been preserved, and 

 which doubtless once formed the connection with the anterior 

 articulation of the following segment. From the above cir- 

 cumstances the segments of this part of the body must 

 necessarily have been much narrower in front than behind, 

 and in all likelihood they bulged considerably towards the 

 middle as in the allied Slimonia acuminata (Fig. Ic). 



The knowledge obtained from the study of the above 

 specimen is of material help in explaining the formation of 

 the so-called " Adam's Plates." These have been produced 

 by corresponding segments to that described of various 

 Pterygoti, but which show no characteristics by which they 

 can be relegated to any particular species. The relation of 

 the specimen above described to the matrix in which it is 

 embedded, throws a good deal of light on the manner in 

 which it became entombed and fossilised. As already stated, 

 the segment, being one of the last five, is a broad closed ring, 



