146 Illinois State Laboratory of Natural History. 



a hyaline lamina ending in a pointed spine-like projection; 

 and the second basal segment is tuberculate at the inner 

 margin, as is also the outer margin of its inner ramus. All 

 of these differences are quite constant but not of sufficient 

 importance to constitute even a variety. 



D. pallidus was found in immense numbers in connection 

 with D. siciloides Lilljeborg during the entire time of my stay 

 at the Biological Station at Havana — that is July and part of 

 August, 1896. So far as I was able to ascertain, siciloides 

 was slightly the more abundant, but the difference was not 

 Very evident. 



Herrick's original description of D. pallidus ('79) was very 

 indefinite, and the establishment of the species really dates 

 from 1893, when Marsh figured and described it in a manner 

 to make it recognizable by later students. De Guerne and 

 Eichard ('89b) place it among their "species insufficiently 

 described." 



Diaptomus albuquerquensis Herrick. (PI. XXYIL, Fig. 

 2, 4.) 



Diaptomus albvquerquensis, Herrick. '95, p. 45. Fig. 16-26. 

 Diaptomus albuqurrquensis, Herrick and Turner, "95, p. 67, PI. VI., 

 Fig. 1-3; Pi. VII., Fig. 1-11. 



A medium-sized species. Cephalothorax widest about the 

 middle. Suture between head and thorax distinct. Last 

 two thoracic segments, seen from above, indistinctly conflu- 

 ent, the last one produced laterodorsally and armed on each 

 side with two rather long spines ; in the male produced but 

 but very slightly and armed with only one spine on each side. 

 First abdominal segment in the female longer than the 

 remainder of the abdomen, dilated laterally, and armed on 

 each side with a single spine ; second and third segments 

 subequal; each shorter than the furcal rami, which are 

 barely twice as long as wide and hairy within. First abdomi- 

 nal segment in the male short, a little more than half as long 

 as any one of the succeeding three segments ; dilated very 

 slightly, and armed on each side with a spine; fifth segment 

 about as long as the first. Furcal rami barely twice as long 

 as wide and hairy within. 



