EURYPTERUS SCOULERI. 



135 



thickened, and raised all round. The ornament of the surface is minute in front, and 

 consists of small prominent tubercles, with minute granules between them ; further down 

 the sides the tubercles become triangular squamae, with others interspersed ; and these 

 squamae become larger and larger towards the ears (with raised borders, and generally a 

 strong central tubercle), and attain their largest size on the posterior area, where they are 

 also narrower and more pointed, as well as stronger, than elsewhere. On the extreme 

 hinder border they become linear ridges, and in this form they also occur on the free 

 edges of the body-segments. The crust is not thick ; and the squamae, except in the 

 largest, appear to be more convex and prominent beneath the crust than above it, so as to 

 indent the cast. This is particularly the case with the smaller squamae, which are so 

 concave above as to be truly convex below ; the margin shows this conspicuously, and 

 wherever the surface has been abraded or weathered, the hollows are much deepened and 

 exaggerated. 



" The body-rings have a great convexity, as above stated ; the two anterior rings are 

 very short, not more than [f ths] of an inch long even in this large specimen. On the under 

 side they expand into the broad sternal flaps so characteristic of this family of Crustacea. 

 One of the swimming-feet is [partially] preserved. The basal joint is either very small, 

 compared with that of Pteri/gotus, or is imperfect. The shape of the other three is not well 

 defined ; but they are evidently thick, carinate at the edges, and have the usual triangular 

 or wedge-like shape alternately in the lower joints." 



Fig. 41. — Under side of head of Eurypterus Scouleri, Hibbert. 

 From specimen in Mr. James Powrie's collection. 



In Dr. Hibbert's description of Eurypterus Scouleri, he says (' Trans. Royal Soc. 

 Edinb.,' vol. xiii, p. 281) : — " The Eurypterus Scouleri is to be distinguished from other 

 species by the prolonged eminences intervening between the eyes, which, at their apex, 



