1094 NEW YORK STATE MUSEUM 



t 



and its posterior edge forms a broad lobe; the sternal portion 

 is short, and its posterior edge is straight, while its anterior 

 edge extends forward to meet the last sternite of the preab- 

 domen. The following five segments are plain, bandlike rings, 

 decreasing in breadth backward. In the first the breadth is 

 considerably greater than the length; in the last, or penultimate 

 body segment the length and breadth, in compressed specimens, 

 are equal. The anterior end of each of these segments is 

 marked by a groove for the attachment of the inter articular 

 membrane. 



The telson is very slenderly lanceolate, widest near the an- 

 terior end and attenuated at the tip. In length it is equal to 

 the four preceding segments. The dorsal surface is convex, 

 rising from sharp, lateral edges to a median longitudinal carina, 

 which begins in the anterior part as a broad, angular promi- 

 nence; the ventral surface is nearly flat or faintly convex; a 

 cross section is thus subtriangular. Compression usually 

 flattens the sides and thus hightens the angular appearance. 

 The uncompressed specimen [pi. 15, fig. 6] has a length of 

 31 mm and a greatest breadth of 7 mm. 



On the ventral surface of the cephalothorax, in front, is a 

 convex lobe or platform, the epistoma, from which extends a 

 flat, tapering doublure ending in a small expansion at the genal 

 angles [pi. 11, fig. 6 and pi. 12, fig. 2]. In molting and also 

 from compression, the epistoma divided through the middle 

 rather than along the sides [pi. 12, fig. 2]. 



Appendages. The preoral appendages are short, stout, three 

 jointed, chelate organs attached at the posterior border of the 

 epistoma [pi. 11, fig. 7]. The two distal joints of each form a 

 pair of broad based, edentulous, bevel-edge pincers, in the ordi- 

 nary state of compression having a breadth equal to one half the 

 length. The blades are about equal in length to the basal por- 

 tion and meet at the very acute, slightly curved tips and again, 

 usually, only near the base. There is considerable variation in 

 the relative form of the pincers, as shown on plate 11. 

 The broad basal joints are about one fourth longer than the pin- 

 cers, widest near the base and longest on the inner side, and in 



