308 



PALEONTOLOGY OF NEW-YORK. 



The first joints of this last pair of feet are broad subrhomboidal plates, already 

 noticed as covering the posterior half of the carapace, the adjacent edges of which 

 are serrate for the purposes of manducation. The second joint is short and stout, 

 and articulated to the first one by a strong process. The third joint is very short. 

 The fourth joint is usually equal to, or longer than the two first. The fifth and 

 sixth joints are smaller. Tlie seventh joint is suddenly dilated, wider and longer 

 than the preceding, rhomboidal, having the penultimate joint articulated close to 

 its distal anterior margin; while along two-thirds of its width there is a tri- 

 angular piece attached by a soldered suture*, the sloping edge of which forms 

 one bide of the pincer-like chela. The eighth joint is subovate, rarely narrower 

 at its upper extremity, and articulated nearer to its anterior edge; so that in its 

 motions, it had the inner cutting edge placed against the sloping side of the tri- 

 angular process of the preceding joint : thus the inner adjacent edges of these 

 parts were fitted to move over each other as the blades of a shears, one being 

 relatively fixed and the other free. The extremity of the last joint is bilobed at 

 the tip for the articulation of a terminal palette, as shown in the figure. 



In the articulation of the joints of these appendages, there is much more 

 freedom at the base of the seventh joint, which, with the succeeding one, forms 

 a prehensile chelate extremity of peculiar character. 



The post-oral plate appears to be attached simply by the muscles to the parts 

 below. 



The first or double segment of the body on the lower side, with its appendages, 

 sometimes occurs separated from other portions of the body; as in the accompanying 

 figure, which is copied from one of these separated joints. 

 Fig. 3. 



The nnchylotcd first and second segmenU 

 of the body, 1 & 2. The suture »» marks 

 the line which, on the back, is the articu- 

 lating line of the two segments. 



The parts a a are two intercalated pieces 

 joined by sutures to the- other parts, the 

 out«r suture lines not reaching to the upper 

 edge of the segment. 



bf the first joint of the locomotive ap- 

 pendage. 



c, the second j( int of the same. 

 d df the extreme free appendcgcs of this organ. 



In the centre of the upper division of this joint are inserted two pieces, leaving 

 a triangular space or emargination behind, into which the locomotive appendage is 

 inserted and joined by sutures : although dividing the lower half of the articula- 



• I infer this to be a guture from the fact that there is always a visible dark line along the junction, and 

 an apparent slight thickening of the substance left in the stone, while the parts arc not unfrcijuently sepa- 

 rated along this line. 



