Copepoda Found in ihe Vicinity of Lincoln, Nebraska. 125 



the outer aspect are two spines, one twice the length of the 

 other, and half the length of the claw. 



The antepenultimate joint of the male right antennae is 

 armed with a hook shorter than that of D. siciloides. 



The basal joint of the male right fifth foot is large, and 

 produced at its distal outer angle into a strong spine. This 

 spine is usually separated from the basal segment by a joint, 

 but I think not always. The inner ramus is much reduced, 

 about equaling in length the spine just mentioned. The 

 terminal joint is long and slender. The accessory spine is 

 slightly nearer the distal end of the segment. The claw is 

 not much curved, and is dentate for half its length. 



The basal segment of the left foot is nearly square. At 

 the outer distal angle there is a small seta. The inner ramus 

 is longer than the first joint of the outer ramus and unarmed. 

 The terminal joint bears a finger-like process and curved 

 ciliate spine opposed to it. On its inner aspect is a nearly 

 hemispherical hairy pad. The left foot does not reach to the 

 end of the basal joint of the right foot. 



This species appears for a short time only in the early 

 spring in stagnant water. 



Diaptomus siciloides Lilljeborg. 



The smallest species of the genus in the locality and one of 

 the smallest anywhere found. It measures less than a milli- 

 meter, but varies somewhat according to its environment. 

 The first segment is two-fifths of the remainder of the 

 cephalo-thorax. The others are equal up to the last, which is 

 somewhat shorter, and bears two small teeth on its exterior 

 angle. 



The first segment of the abdomen more than equals the 

 last two and furca. It bears a small lateral tooth. The second 

 segment is about one-third of the last. The furcae are longer 

 than broad, and are ciliated on their inner margin. 



The antennae reach nearly to the ends of the furcal setae. 



The male antennae are not strongly geniculate. The ante- 

 penultimate joint of the right antenna bears a hook longer 

 than that of D. sanguineus or saltillinus. It is nearly half as 

 long as the following joint. 



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