164 Illinois State Laboratory of Natural History. 



"Length of female, 4 mm. ; of male, 3.5 mm. 



"Found, near Fresno, Cal., by G. Eisen, the Swedish zoolo- 

 gist, member of the San Francisco Scientific Academy." 



"This Diaptomus is dedicated to Mr. G. Eisen, who found 

 it in California with a great number of other Entomostraca. 

 It was given by him to the Zoological Museum of the Uni- 

 Tersity of Upsala. D. eiseni is very distinct from all the 

 American species described by Profs. Forbes and Herrick."* 



The last thoracic segment of the female is strongly pro- 

 duced posteriorly and the first abdominal segment is moder- 

 ately dilated and armed on each side with a large spine. 

 This form may also be recognized on account of its great 

 size, being but little smaller than D. stagnalis or 1). shoslione 

 Forbes. The fifth pair of legs are remarkable for the ex- 

 treme size of the inner of the two spines representing 

 the third segment of the outer ramus, which is made still 

 more striking by a row of strong teeth on each margin. The 

 second segment of the outer ramus is also armed with strong 

 teeth on the inner margin. 



The fifth pair of legs of the male may be easily recognized 

 from the fact that at least an indication of a suture is found 

 on each inner ramus, making it indistinctly two-segmented. 

 The rugose lamella on the second basal segment of the right 

 fifth leg is also very characteristic. 



Diaptomus signicaudaLiLLjEBOEo. (PI. XXIX., Fig. 3-6.) 



Diaptomus signicauda, de Guerne et Richard, 'S9b, p. 55, PI. I., Fig. 



15,16,31; PI. III., Fig. 22. 

 Diaptomus signicaiidatus, Herrick and Turner, '95, p. 63, PL VIII., 



Fig. 13; PI. IX., Fig. 10. 



"This species is among the smaller species of this genus. 

 Form of the body very slender. Cephalothorax widest in front 

 of the middle, at the second segment. Last two segments of 

 the thorax (PI. XXIX., Fig. 6) confluent above, the last, seen 

 from alcove, with rather large and projecting lateral lobes, 

 posterior angles acute, with small spines. Fourth thoracic 

 segment, seen from the side, provided above with a small 



*LiUjeborg's description luid remarks from de Guerne et Richard. "SOb. 



