1914.] NATURAL SCIENCES OF PHILADELPHIA. 29 



inner ramus of the fourth foot, already mentioned. I quote from 

 her paper once more. ''He (Herrick) states that the two varieties 

 have similar armature of the swimming feet, but that tenuicornis 

 iliffers from coronatus in the absence of serrations on the antennal 

 lamellae and in the divarication of the ovisacs." Here follows the 

 original description of Herrick's "Cyclops signatus var. tenuicornis. 

 First segment of thorax shorter, its length to that of the entire thorax 

 as 1 : 1.9. Last segment of antennse with unserrated lamella. 

 Caudal stylets longer, length to width as 2.1 : 1, inner aspect not 

 ciliated. Outer apical seta half as long as inner. Second segment 

 of antennules longer. Color variable, but always banded or 

 splotched. It is also generally true that the ovisacs in the present 

 variety are more strongly divaricate than in the variety coronatus." 

 ]\Iiss Byrnes now concludes that since "the antennal lamella of 

 anjiidicornis sometimes bears serrations and coronatus sometimes 

 bears its egg masses in a divaricate position, as I have found in 

 attempting to distinguish the two forms by this character, .... 

 consequently Herrick's diagnosis is untenable." This gives Herrick 

 absolutely no credit for six of his eight points of difference noted. 

 Herrick's diagnosis should not be considered untenable, but merelj- 

 incomplete. 



This species, while not as common as Cyclops albidus, appears to 

 be quite generally distributed over the United States. Forbes 

 reports it from the "ponds and lakes of Wisconsin, Michigan, Illinois, 

 and Massachusetts," where it "occurs sparingly." Brewer found 

 it with C. albidus Jurine (= C. signatus var. tenuicornis Herrick) in 

 the vicinity of Lincoln, Nebraska, but "always in small numbers." 

 Miss Byrnes has studied the species at Cold Spring Harbor, Long 

 Island. Kofoid does not mention it in his studies of the "Plankton 

 of the Illinois River." I have found it in this locality; rather more 

 abundantly in September, October, and April than during the winter 

 months. I have never found it in very great numbers. During 

 the summer and fall of 1909, it occurred sparingly in collections 

 from Lake Winnepesaukee, N. H., and in a small pond adjoining 

 "Fresh Pond" at Cambridge, Mass. 



Specific Description. — The cephalothorax (PI. I, fig. 1) in this spe- 

 cies is a little more than twice as long as the abdomen. They are to 

 each other as 21 : 10. The first segment is to the entire cephalothorax 

 as 7 : 11. The length of the thorax to its width is as 11: 6. In the 

 living animal none of the lateral angles of the thoracic segments are 

 prominent. The posterior borders of the thoracic segments are all 



