52 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 



This species was first noticed in America by the writer, in an ap- 

 pendix to his paper in the twelfth annual report of the state geologist 

 of Minnesota. Careful study of abundant material since then shows 

 the identification well-founded, although a few slight differences be- 

 tween this and the north European species can be detected which are 

 by no means so great as the variations in the figures of the several 

 European authors who have described the species. Should it prove 

 that this like other Calanidce is dimorphous T. clausii may disappear 

 and the old name T. velox will then be restored for both forms. 



Claus is certainly in error in calling the fifth pair of feet four- 

 jointed, as shown by his own figures and especially those of Poppe. 

 Great interest attaches to this find, because it seems to indicate that 

 the same morphological species has arisen under similar conditions in 

 isolated stations. Should the species be found along the Atlantic 

 coast, however, this assumption will be unnecessary. 



The curious resemblance, amounting almost to identity, between 

 the Temora armata of Claus and Brady's T. dubia is likewise instruct- 

 ive, leaving very little doubt of close genetic relationship. 



Boeck's description of T. inermis is here translated for the sake of 

 completeness. (See Oversigt over de ved Norges Xyster iagtlagne Cope- 

 poder; Vidensk. Selskab. Forhandlinger, 1864, p. 16.): 



Length about 1.50 mm., transparent, colorless, with yellow viscera 

 and a yellow band on the posterior part of the head and another upon 

 the first segment of the abdomen. The body greatly elongated, slen- 

 der. Head divided by a transverse suture into two parts, likewise 

 the fourth and fifth segments distinctly separated. The fifth segment 

 in the male rounded, in the female accuminated. The first joint of 

 the abdomen in the male, but the middle one of the female, the short- 

 est. The caudal appendages elongate, but shorter upon the abdomen 

 of the male. The outer seta attached nearer the middle than the- end 

 of the caudal stylets. The anterior antenna of the male is strongly 

 swollen in the middle and is armed with small spines upon the eighth 

 to the twelfth joints. Last foot of the female two jointed, first seg- 

 ment short; second longer, oval, provided on the outer angle with a 

 spine, on the inner with a longer curved spine-like process, at the 

 apex is a long, straight spine. The fifth legs of the male are three- 

 jointed; second joint of left limb shortest, the third expanded at the 

 end; first joint of the right foot long, but less broad; spines on the 

 inner angle very small; third segment rather longer and provided at the 

 end with simple teeth. 



The Temorella (Eurytemora) hlrundo of Giesbrecht differs from T. 

 affinis on\y in three very significant particulars: first, the body is more 

 slender; second, the caudal stylets are considerably longer; third, the 



