80 PPP. KEroKT OF i'iu)c;kkss. .ia.mks hall. 



MEROSTOMATA. 



EuuYPTEKUS, Dekay, 1825. 



EuRYPTERUs Bi:eciieri, n. sp. 



Plate III, Fig. 1. 



Carapace unknown. Body elongate, very convex along 

 the dorsum, composed of twelve free segments wliich grad- 

 ually increase in breadth from the head backwards to the 

 fifth somite, from whence they rapidly decrease in width 

 and increase in length, until the eleventh segment has a 

 length equal to half its Avidth, while in the fifth segment the 

 breadth is four times its length. Lateral margins of the 

 segments flattened, and slightly extended backwards on 

 the post-lateral angles, forming a mucronate projection. 

 The posterior tergal margin of each somite is ornamented 

 with several triangular scales or nodes, pointing towards 

 the telson. The number of these nodes on each segment 

 decreases from the anterior segment, which has eight or 

 more, to the tenth somite which is furnished with six. The 

 number on the two posterior segments is not known, on ac- 

 count of their imjDerfect preservation in the specimen de- 

 scribed. 



Two joints of one of the great swimming feet are pre- 

 served, which are remarkable for their great length and for 

 three or more strong longitudinal carinse ornamenting them. 

 The distal joint of the two has a length of more than three 

 times its breadth, while the other has a length of nearly 

 five times its breadth. These joints are probably the third 

 and fourth from the attachment of the limb and correspond 

 to the basos and ischium of a typical decapod. Telson and 

 other appendages unknown. " 



The twelve free segments of the body have a total length 

 of 96 mm., and the width of the fifth segment is 41 mm. 

 The body measures 39 mm. across at the first segment and 

 25 mm. at the tenth. The longer joint of the natatory ap- 

 pendage has a length of 30 mm. 



The specimen from which the present description is taken 

 was found in a bed of fine grained sandstone occurring in 

 the Chemung group at Warren. Although lacking many of 



