1096 NEW YORK STATE MUSEUM 



long as the joint proper, marked off from the inner, distal end 

 by a suture. The eighth, or palette, is elongate oval with the 

 margin finely incised, and carries the minute claw inserted in a 

 notch on the inner side near the tip. On the dorsal surface of 

 the seventh and eighth joints, at the proximal end and outer 

 edge of each, is a group of minute, craterlike tumescences, which 

 were probably receptacles for the bases of hairlike bristles 

 [pi. 14, fig. 8]. In a swimming arm 29.5 mm long, exclusive 

 of the gnathobase, the narrowest joint or the fourth, measures 

 5 mm across; from this point the arm gradually enlarges to 

 6.8 mm on the seventh and eighth joints. When the swimming 

 arms are turned back, they reach the line of the fourth or fifth 

 dorsal segment. The gnathobases have the form of an upright 

 retort. The inner extremity of each is provided with from 18 

 to 20 sharp, slightly curved teeth, which become finer posteri- 

 orly. A gnathobase, accompanying a cephalothoracic shield 

 22 mm long, is 16 mm long; the width of the narrow necklike 

 portion 6 mm; the width at the base 13 mm. 



The metastoma is elongate cordate, the greatest breadth com- 

 ing anterior to the middle. The smaller, or posterior end, is 

 truncated and has rounded corners. The anterior notch is 

 rather deep and broad. A comparison of the length to the 

 greatest breadth of several metastomas gives the proportion of 

 2:1. In an individual having a cephalothorax 23 mm long the 

 metastoma is 16 mm long. 



The genital appendage differs noticeably in the two sexes. In 

 the female it consists of two parts, one carried by the operculum, 

 the other by the second sternite [pi. 13, fig. 1, 2]. The opercu- 

 lar appendage is a slender, sagittate-based, convex, scalelike 

 sheath projecting for about one fifth its length beyond the 

 posterior edge of the operculum and appearing to be formed 

 by the fusion of two parts. The anterior of these includes 

 the sagittate base and a narrower, more convex portion with 

 a flattened border on either side [pi. 13, fig. 4]. Its distal end is 

 reentrant [pi. 24, fig. 1] and fused to the posterior part. This part 

 is a little narrower, slightly tapering and beveled in from 

 either side for one fourth the breadth, to the sides of a slightly 

 raised platform which is flat topped for the greater part of its 



