832 



VBOCEEDINGS OF THE NATIONAL MUSEUM. 



12. DYNAMENE Leach. 



ANALYTICAL KRY TO THK Sl'ECIKS OF DYNAMENE. 



a. Fioiitiil margiu of head produced in a (luadrangular process; first two joints of 



(iist pair of antenna', dilated 21. Djinavienc dilatata, new species. 



a'. Frontal margin of head not produced; Joints of first pair of antennai not dilated. 

 b. Abdomen tuberculated. Neither branch of uropoda reaching extremity of abdo- 

 men 22. Dijnamene tuhcrmiloaa, now siiecies. 



b'. Abdomen not tuberculated. Inner branch of uropoda reaching extremity of 

 abdomen, 

 c. Ultimate segment of abdomen ridged. Branches of uropoda of equal length. 

 Sinus at extremity of abdomen funnel shaped. 



23. Dynamene benedicti, new species. 



c'. Ultimate segment of abdomen smooth. Outer branch of uropoda but little 



more than lialf as long as inner branch. Sinus at extremity of abdomen 



small 24. Dynamene ylabra, new siiccies. 



It has been .suggested by several authors ' that Dynamene may prove 

 to be the female of Ncvsa, but until facts cau be produced to substan- 

 tiate this assumption, it is necessary to retain the genus Dynamene. 



21. DYNAMENE DILATATA, new species. 



Body oval; surface very granular; color yellow. 



Head rugose, with its anterior margiu produced in a quadrangular 

 process, having a small median projection, 

 rounded antero-lateral angles and a thickened 

 edge. First pair of antenmc extend to the 

 posterior margin of the head, first two joints 

 flattened and enlarged; first joint oblong, sec- 

 ond joint triangular, and half as long as pre- 

 ceding joint; third joint small, as long as sec- 

 ond, but half as wide; flagellum six-jointed. 

 Second pair of anteume are but little longer 

 than first pair and do not reach the posterior 

 margin of the first thoracic segment. 



The thoracic segments are of equal length. 

 The epimera are square or oblong, with straight 

 lateral margins. 



The penultimate abdominal segment is short, 

 and crossed with suture lines. The terminal 

 segment is triangular with a small rounded 

 notch at the apex. There are three longitudi- 

 nal ridges on the segment, one in the median 

 line, and one on either side of it. The uropoda 

 are short, not reaching the extremity of the abdomen, and regularly 

 rounded. 



The legs are slender; the first two pairs are covered with long hairs. 



Fig. 8.— Dynamene dilatata. 

 o, head and first tnoracic 



SEGMENT. X 13i. b, DORSAL 

 VIEW. X lOf . 



'Hesse, Ann. Sci. Nat., 5th ser., XVII, pp. 5, 6; Stebbing, Hist, of Crust., 1893, 

 p. 361; Bate and Woetwood, British Sessile-Eyed Crust., II, p. 432. 



