WATERLIME GROUP. 411* 



This species has been referred to E. lacustris, and the resemblance is very close. 

 The form of the anterior feet and the swimming feet are essentially the same, while 

 the joints of the body are proportionally longer and stronger; furnishing sufficient 

 ground for a variety, but-not satisfactory evidence of specificdifference. 

 Fig, 1 View of the specimen from the lower side. 



Geological position and locality. In the Waterlime group, near Buffalo. 



EurjTiterus dekayi (n. s.). 



Plate LXXXII. Fig. 1. 



Carapace semicircular, length being to the width as 11 to 19, anteriorly 

 and laterally margined by a slightly elevated rim. Body broad, ovato- 

 lanceolate ; length, including the tail-spine, a little more than twice 

 and a half the greatest width ; width across the thorax greater than 

 the base of the head, gently narrowing at the fifth and sixth segments, 

 and below this more abruptly contracted. The first six segments are 

 plain, and rounded at their lateral margins ; those below are imbricate 

 with mucronate extensions, while the last'one is alate on each of its 

 lateral edges, and is extended at its posterior angle in mucronate or 

 spiniform processes over the base of the tail-spine. The abdominal joints 

 gradually increase in length to the eleventh, and the twelfth is twice 

 as long as the preceding. The tail-spine is triangular, as long as the five 

 preceding joints, and, in its present condition, concave along the upper 

 side, with the angles apparently free from serrations. 



PosTOKAL PLATE suboval, greatest width a little above the middle, the an- 

 terior end concave. The pairs of feet originate a little anterior to the 

 middle of the carapace : the basal joints are short ; the maxillary 

 plates broad and strong; the coxa is wide and short (the succeeding 

 joints are not discernible in the individual) : the fourth, fifth, and 

 sixth joints have their distal angles strongly mucronate ; the seventh 

 joint is abruptly dilated, comparatively broad and short, while the 

 movable chela is likewise short and broad, and the terminal palette 

 small. The central thoracic appendage reaches to the fourth articulation, 

 with the terminal processes short. 



