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



649 



DIASTYLIS ARGENTATA, new species. 



Ovigerous female. — Total length, 7.7 mm. (Females, apparently 

 adult, varied from about 7.5 to about 9.5 mm. in length.) 



Carapace less than one-third of total length, its height two-thirds 

 and its breadth more than three-fourths of its length; seen from 



Fig. 70.— Diasttlis argentata, female, feom the side. 



the side, its dorsal outline is moderately arched, with a distinct 

 notch at the base of the pseudorostrum, which is horizontal and 

 acute. The surface of the carapace is rather coarsely pitted; there 

 are a few denticles on the dorsal side of the base of the pseudorostrum 

 and a curved lateral line of denticles runs backwards 

 for a little way on each side from the pseudorostrum. 

 Just above the lower edge of the carapace at about 

 one-third of its length from the front is a small pro- 

 curved tooth. A rounded tubercle from wliicli a 

 slight ridge runs forward marks the posterior end of 

 each branch of the frontal fissure, and just internal 

 to it is a deep pit. The ocular lobe is small, with- 

 out distinct ocular elements- 

 There is no antennal notch and 

 the anterior part of the lower 

 margin of the carapace is 

 rather coarsely serrated. 



The surface of the bod}'-, and 

 especially of the carapace, has 

 a silvery nacreous luster. 



The pleural plates of the second and third 

 free thoracic somites are rather coarsely serrate 

 anteriorly. There are a few minute denticles 

 on the dorsal surface of the last three thoracic 

 somites, and the hinder edge of the fourth 

 somite is crenated. The postero-lateral lobes 

 of the fifth somite are rounded, as seen from above, and each tipped 

 with a small denticle. 



The abdomen (excluding the telson) is a Httle shorter than the 

 cephalothoracic region; the first somite has a pair of dorso-lateral 



Fig. 71.— Diastylis 

 argentata, fe- 

 male, anterior 

 part of body from 



ABOVE. 



Fig. 72.— Diastylis argentata, 



FEMALE, first LEG. 



