NorfJi Am('7'ic(in S2)eci('s of Diaptumiis. 151 



The above description is compiled from Herrick's first 

 paper on this species ('95) and from the figures and the 

 English and Latin descriptions in his later paper (Herrick 

 and Turner, '95). Both of these articles are published as 

 original descriptions, although there was nine months' differ- 

 ence in the time of their appearance. 



Diaptomus oregonensis Lilljeborg. (PI. XXIX., Fig. 



1, 2.) 



Diaptomus oregonensis, de Giierne et Richard. '89b, p. 53. PI. II., Fig. 



5; Pi. 111.. Fig. 8. 

 Diaptomus 07-eijo7iensis, Marsli, '93, p. 200, PI. IV., Fig. 4, 5. 

 Diaptomus oregonensis, Marsli, '9.5, p. 8, PI. VII.. Fig. 5. 

 Diaptoimts oregonensis, Herrick and Turner, '95. p. 72, Pi. IV., Fig. 



7-12; PI. IX., Fig. 3. 



A species of medium size. Cephalothorax widest about 

 the middle. The last two thoracic segments confluent above, 

 the last one, seen from above, slightly produced laterally, 

 bluntly rounded but unarmed ; in the male armed with two 

 very minute spines on each side. Fii'st abdominal segment 

 as long as the rest of the abdomen.* Third segment and 

 furcal rami subequal, the latter about one and a half times 

 as long as broad and delicately hairy within. In the male 

 the first abdominal segment is short and unarmed ; second 

 and third segments and furcal rami about equal ; fourth 

 segment the longest, about equal in length to the first two 

 segments taken together. Furcal rami about as in the female. 



Antenna of the female '25 -segmented, extending beyond the 

 tips of the furcal setfe. Prehensile antenna of the male but 

 slightly swollen, the antepenultimate article entirely unarmed. 



First basal segment of fifth leg of female (PI. XXIX., Fig. 

 2) with the usual delicate hair on the outer margin. First 

 segment of outer ramus about twice as long as wide, slightly 

 arcuate, margins parallel ; second segment about as long as 

 the first, moderately curved, terminating in an acute point, 



*This segment had a very peouliar appearanoe. Owins to the thicker anterior 

 part, the setrnient seemed to "have a suture at about the middle, and this was so mis- 

 leading that I doubted if tlie si)eclmens on the slides were really females until I could 

 see the antennae, and not until I could get a side view was I at all ceitain that there 

 was only one segment. 



