CRUSTACEA OF ALABAMA. 15 



mature. The fifth foot is obscurely 3-jointed, the second joint bearing a short spine and 

 the terminal joint two spines of varying length. The stylets are once and a half as long 

 as the last segment and are peculiarly excavated for more than the lower third, from the 

 point where the lateral spine is situated. The outer terminal seta is short, the others 

 being sub-equal and also short. The opening of the spermatheca is elongated, oval. 

 The antenna of the male is divisible into five regions, the third being formed by the 

 thickening and coalescing of four or more segments. 



Cyclops fluviatilis, Hemck. 



Cyclops magnoctavus, Cragin. A contrib. to the History of the Fresh-water Copepoda. Trans. Kansas 

 Academy of Science, May, 1883. 



This small species, although apparently restricted to America, is one of the most 

 abundant forms in the larger lakes and especially in streams. In its smaller age-form it 

 is barely visible to the eye, while the larger and particularly the higher colored condition 

 is readily distinguished. In appearance it somewhat reminds one of Cyclopsina gracilis. 

 The species was first described by the writer in 1882, in the Tenth Annual of the Minne- 

 sota Geol. Surv. 



The full grown female measures about .70 mm, but the greater number of adult in- 

 dividuals measure only about .55 mm. In a specimen measuring .57 mm, to the end of 

 the stylets, the following proportions were noted : First segment of thorax .22 mm, sec- 

 ond and third segments each .056, fourth .032 ; the total length of abdomen .17, stylets 

 .032 mm. The longest seta measured .128 mm, the outer median .10 mm. It will be 

 seen from these figures that the form is slender and the first thoracic segment propor- 

 tionally much longer than in any other species of the genus. In this respect as well as 

 in the armature of the swimming feet the species approaches the calanidse. The anten- 

 nae are nearly as long as the whole thorax, and are remarkable for the elongation of the sev- 

 enth to ninth segments. There are long setae upon the first and fourth segments. The 

 last joint of the antennae is hinged, and apparently ornamented with a slight ridge, and, 

 together with the next following, is slightly curved outward. The antennules are elong- 

 ated and slender. The labrum has about twelve small teeth. The maxillae have the 

 usual form. The feet are peculiar in the exceedingly long setae. The armature of the 

 terminal segments of the first, third and fourth pairs of feet, is as follows : 



Outer ramus. Inner ramus. Outer ramus. Inner ramus. 



I. ex. 3 spines. ex. 1 seta. ex. 3 spines. ex. 1 seta, 



ap. 2 setae, ap. 2 seta;. III. ap. 1 spine, 1 seta. ap. 2 setae, 



in. 3 setae. in. 3 setae. in. 4 setae. in. 3 setaa. 



Outer ramus. Inner ramus. 



IV. ex. 2 spines. ex. 1 seta. 



ap. 1 spine, 1 seta. ap. 1 spine, 1 seta, 



in. 4 setae. in. 2 setae. 



The fifth foot is small, one-jointed and bears three small setae. The abdomen is 

 slender though rather short. The stylets are about three times as long as broad and are 



