17 



III. On New Species of Eusarcus and Pterygotus from 

 the Water Lime Group at Buffalo 



BY AUG. R. GROTE AND W. H. PITT. 



[Read before tJiis Society, 8ex>temher 3, 1875.] 



The dorsal surface of a species belonging to the genns E^lsar- 

 cus Grote and Pitt, is exposed in a specimen from the same beds 

 from which the type of the genus, I£. scoy'pionis, was procured. 

 The new species, for which the name EiLsarcus grandis is pro- 

 posed, is apparently one of the largest fossil Crustaceans known 

 from our Water Lime Group. Four segments of the abdoinen 

 are distinctly shown in the specimen. As compared with the 

 specimen of E. scorpionis, these are the fourth, fifth, sixth and 

 seventh segments of the animal ; the last named segment being 

 the one preceding the narrow caudal segments in this genus. 

 This is determined by the shape of the seventh segment. A 

 trace of the first caudal segment is seen, medially, in the speci- 

 men. The fourth and fifth sogments overlap a little on the right 

 side. The sixth is partially displaced and imbedded in the ma- 

 trix. The seventh is in position and completely shown. The sur- 

 face is roughened with scattered, irregular, somewhat rounded- 

 heart-shaped tubercles, which are more thickly massed along 

 * the middle of the segments ; these latter are smooth, perhaps 

 worn along the margins. The fourth and fifth show a mesial 

 line along which the tubercles are gathered. The fourth seg- 

 ment has become, in the specimen, narrowly separated along this 

 line in front. The length of these segments in the specimen is 

 Q^ inches ; in E. scorpionis the same segments measure 2f inches. 

 From these data the total length of the animal would be about 



BUL. BUP. SOC. NAT. SCI. (3) SEPTEMBER, 1875. 



