126 



Cincinnati Society of Natural History. 



The species is recognized readily by a projecting knob on 

 the inner margin of the first joint of the outer ramus of the 

 male right fifth foot. The inner ramus is half as long as the 

 first joint of the outer. Half its length is covered with fine 

 hairs. The accessory spine is at the last third of the termi- 

 nal joint. The terminal claw is regularly curved, and without 

 dentition. 



The basal joint of the left foot is produced in the direction 

 of the inner ramus, which reaches the middle of the terminal 

 joint of the outer ramus. The two joints of the outer ramus 

 are ciliated on their internal aspect. The end of the terminal 

 joint is covered with fine teeth. It bears two short blunt 

 processes, one at the tip, the other at the last fourth interi- 

 orly. 



The inner ramus of the fifth foot of the female has a pointed 

 tip covered with fine hairs. At the inner side of the tip are 

 two curved spines or setae one half the length of the other. 

 The terminal claw is not much curved, but is dentate on the 

 inner margin, and sometimes on the outer. 



This species is found everywhere about here by itself or in 

 association with any of the other forms, in large lakes and 

 stagnant pools, and at all times of the year. 



Diaptomus sai/tilunus n. sp. (Figs. 5-9.) 



The species is of medium size and quite slender. Its first 

 segment equals about two-fifths of the cephalo-thorax. The 

 following are not quite equal to each other, but gradually 

 decrease in length to the last. 



The female has a broad short spine in the middle of the 

 back of the next to the last segment of the thorax, which 

 serves to easily distinguish the species. The last segment is 

 distinctly asymmetrical, the left side projecting back and out 

 further than the right. There are small spines, outwardly 

 directed, at both the inner and outer angles of the projecting 

 part. 



The first abdominal segment of the female (Fig. 7) is as 

 long as the two following and the furca. It bears small lateral 

 spines on the second fourth. The second segment is very 



8 



