NO. 1876. ON THE CRUSTACEAN ORDER CVMACEA—CALMAN. 



663 



prominent acute antero-lateral tooth, behind wliich the lower edge 

 of the carapace is finely serrated. The ocular lobe is very small and 

 there is no distinct eye. 



The free thoracic somites together are about equal in length to the 

 carapace. The pleural plates of the second somite are rounded in 



Fig. 81.— Diasttlopsis dawsoni, immature female, from the side. 



front, defined above by a narrow notch, and completely conceal 

 those of the first somite. The third and fourth somites are more 

 firmly connected together than they are with tlie adjacent somites, 

 but the line of junction is strongly marked. The third somite is very 

 short in the middorsal line, but its pleural expansions are strongly 

 produced backward to embrace the long fourth somite; 

 the length of these lateral expansions is about one-half 

 that of the carapace. The point of attachment of the 

 third pair of legs is thus carried backward, leaving a 

 long interval between them and the second pair. The 

 last thoracic somite is small and its posterolateral 

 corners are not produced beyond the articu- 

 lation of the fifth legs. 



The last thoracic somite bears a pair 

 of stout curved teeth on the sternal 

 surface and the first abdominal a single 

 tooth. The abdomen, including the 

 telson, is shorter than the cephalotho- 

 racic region. The fifth somite is not 

 longer than . the sixth. The telson is 

 about tliree-fourths as long as the sixth 

 somite, swollen in its basal part. 

 There are about four pairs of slender 

 setif orm lateral spines, and the terminal 

 pair, though stouter, are still unusually 

 long and slender, being about one-third as long as the telson. 



The first segment of the peduncle of the antennules is nearly as 

 long as the second and third together; the third is about half the 

 diameter of the second and longer than it. The shorter flagellum 

 is about equal to the first segment of the longer and is apparently 

 composed of only two segments. The antenna has four segments, 

 the penultimate elongated (about four times as long as wide) and 



Figs. 82-84.— Diasttlopsis dawsoni, im- 

 mature FEMALE. 82, Anterior part of 



BODY FROM ABOVE; 83, ANTENNULE AND 

 antenna; 84, MANDIBLE. 



