NO. 2096. NEW ENTOMOSTRACA FROM COLORADO— DODDS. 



99 



western edge of the great plains, contains an abundance of this 

 species. 



Type-locality. — Sulphide Pool, near Eldora, Colorado. 



TVpe.— Male, Cat. No. 47876, U.S.N.M.; paratype, female, Cat. 

 No. 47876, U.S.N.M. 



Subclass COPEPODA. 



Order EUCOPEPODA." 

 Family CENTROPAGIDAE. 



DIAPTOMUS ARAPAHOENSIS, new species. 



This is a red species of moderate size. The ceplialothorax is mod- 

 erately slender, with its greatest width about the middle (posterior 

 margin of second segment). The last segment is produced posteriorly 

 on either side into a somewhat triangular 

 lob considerable size, less pronounced in 

 the male than in the female. Each lobe 

 bears two small spines, one at the distal 

 angle, and the other at about the middle of 

 the inner dorsal margin. The first segment 

 of the female abdomen is slightly less in 

 length than the two following. Its greatest 

 width is somewhat beyond the n\iddle, back 

 of which it becomes abruptly narrower. It 

 bears two spines on either side, a moderate- 

 sized one at the point of greatest width, and a 

 smaller one about halfway between this point 

 and the posterior end of the segment. The 

 second segment is indistinctly separated from 

 the first, is sHghtly shorter than the third, and 

 its length is slightly less than its width. The furcal rami are a little 

 shorter than the third segment, are cUiated on the inner margin and 

 have a few cilia on the outer margin also. (Fig. 3.) The female an- 

 tennae reach slightly beyond the end of the cephalothorax. The male 

 antennae are relatively longer, reaching beyond the middle of the abdo- 

 men. The male right antenna is moderate!}'' enlarged. Its antepenul- 

 timate segment bears a slender, straight process, which reaches about 

 to the middle of the ultimate segment. (Fig. 4.) The first basal 

 segment of the female fifth foot bears the customary small spine. 

 The lateral hair of the second basal segment is slender. The first 

 segment of the exopodite is a little more than twice as long as broad. 

 The claw of the second segment is slightly smuous, its inner margin 

 is finely denticulate, and its outer margin bears some small spines. 

 There is a small spine at the outer distal margin of this segment. 



Fig. 3.— Diaptomus arapahoen. 

 SIS. Abdomen of female- 

 X50. 



