178 Illinois State Laboratory of Natural History. 



"The description given was sent to" us by Prof. Lilljeborg 

 as that of a new species described by him under the name of 

 D.fresnanus. It was established from specimens found by 

 G. Eisen at Centreville, near Fresno, Cal. J>. tyrrelli here 

 reaches a size somewhat greater than that which it has at 

 Summit Lake, where it is only 1.5 mm. long."* 



Owing to the kindness of Herr Poppe I was enabled to ex- 

 amine specimens of l>. tyrrelli, but found nothing to add to 

 the above description. I failed to obtain specimens from Dr. 

 Lilljeborg, and so am unable to say whether or not there are 

 minor differences to be found in individuals from the two 

 localities in which they have hitherto been found. 



Diaptomus clavipes n. sp. (PI. XXXIV., Fig. 1-3 ; PL 

 XXXV., Fig. 1, 2.) 



Body of about the same width throughout, except at the 

 head and at the last thoracic segment, where it narrows 

 slightly. Last two thoracic segments confluent, the last one 

 with slightly rounded posterior angles, armed on each side 

 with a short blunt spine. In the male the body is less 

 strongly bifid than in the female, and the spines are smaller. 

 There is but slight difference in the length of the abdominal 

 segments (PI. XXXV., Fig. 2), the second segment being 

 longest and about equal to the furcal rami. The first seg- 

 ment is asymmetrical and armed on each side with a thick 

 blunt spine, the one on the right side being the more conspic- 

 uous ; in the male the segment is unarmed. Furcal rami hairy 

 within ; furcal seta- long, slender, and covered with delicate 

 hairs. 



Antenna? 25-segmented, extending beyond the furcal setae. 

 Geniculate antenna of the male (PI. XXXIV., Fig. 2) greatly 

 swollen from the twelfth to the eighteenth segments inclusive. 

 The armature of the segments is as follows : 1 and 7 have a 

 sense-club and a long spine ; 2, two long spines, a sense-club, 

 and a sense-hair; 8, a sense-club and a long seta; 4 and 

 8, a long spine; 5, a sense-club and a short .-eta: 8, a 

 short and a long spine; 9, a short spine, a long seta, and a 



*De Guerne et Richard, '89b. 





