BRITISH FOSSILS. 4,7 



at its base, the lower part barrel shaped, about twice as wide as 

 long, and tapering rather gradually into the serrate portion. The 

 free claw V" is broad, linear, and beset with numerous small teeth, 

 a few larger striated ones interspersed ; the first only is seen on each 

 chela, that on the fixed claw very near the angle ; that on the free 

 finger is more distant.* 



c', c", Mandibles, &c.f There are traces of two pairs of jaws, the 

 palpi attached or in close proximity, figured with the rest of the 

 carapace in Plate XV. fig. 2. One endognath is lying loose on the 

 left hand of that figure in a reversed position, and has the usual 

 curved striate teeth, but nothing can be determined of its shape. 

 On the opposite side two jaws with palps lie one over the other, 

 and a woodcut is added below, Fig. 2, to show in a diagrammatic 

 form the arrangement of these pieces with their appendages. 



The outer jaw, g, shows the terminal serrate lobe, with at least 

 seven articulated arched teeth (the uppermost largest), and about 



FlG - 2 ' * e ll This specimen is 



Pterygotus pcror- A ^MRnRnin&^dHfeild^^ FA the same as that 



- . , M figured in Plate 



bles,0, A; palpi, . ''Y^^^f:^ ll XV. fig. 2, but 



c, h,i, &c. The '&'' '^'~ ^^^\ with some parts 



post-oral plate is ^^^r^ ' ^fef; - ' ^ omitted. 



in situ. ,\7 



three times as long as the breadth at their base, and sharp pointed. 

 The other, k, is pushed in advance of g; it shows a similar set, more 

 displayed, of curved striate teeth ; about five are distinctly preserved. 

 The filament c, I, which, from analogy with that of H. bilobus, is 

 presumed to be the palpus, appears to me to be connected with the 

 mandibular piece g, and to cross the two others, h, i, which seem to 

 form part of a branched palpus, and to belong to a second ectognath 

 (mandible or maxilla). But the connexion of these with the serrated 

 pieces g or k is not quite certain ; they must therefore be described 



* In Pterygotus the large teeth are very nearly opposite one another in the middle and 

 outer portions of the forceps, and must have acted as cutting blades, not merely as 

 prehensile forceps (see Plate VI.) 



f Discovered in this species by Professor Huxley. But he does not agree with me, that 

 there is sufficient evidence of the two pairs of jaws, one with a single, the other with a 

 branched palpus (see p. 23). 



