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 Calanide is dimorphous 7. clausii may disappear 
and the old name 7’. 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 7. inermis is here translated for the sake of 
completeness. (See Oversigt over de ved Norges Kyster iagttagne 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) hirundo of Giesbrecht differs from 7. 
affinis only in three very significant particulars: first, the body is more 
slender; second, the caudal stylets are considerably longer; third, the 
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