STATE GEOLOGIST. 129 



Since writing the above, it is brought to my notice that in April, 

 1881, V. T. Chambers gave some account of a species of the Hai- 

 pacticidse referred b}'' him to Tachidius, This species is particularly 

 interesting on account of its novel habitat. Tachidius (?) fonticola, 

 Cham., is found in the saline waters of Big Bone Springs, Ky., and 

 thus is ver}' distant from any marine congeners. It is perhaps 

 doubtful if the generic reference can be sustained, but the species is 

 worthy of further stud}'. The Diaptomus described by the same 

 author is hardly recognizable. 



FAMILY CALANID^. 



This group is pre-eminently marine and contains diverse and 

 graceful forms mostly with very elongated bodies and antennge. 

 Of the six genera here enumerated as more or less habituated to 

 the use of fresh water, two are found as yet only in America 

 and one is confined to Europt;, 



Heterocope, namely, is verj' near Epischura, both being restrict- 

 ed to fresh water. Diaptomus and Osphranticum are likewise only 

 accidentally found in the seas, though their nearest allies are marine. 

 The genus Limnocalanus is as yet found in America only in the 

 Great Lakes. 



In the distribution of genera we here follow Brady, whose defini- 

 tion of the family Calanidte, including Calanidaeand Pontellidse of 

 authors, we quote: " Body elongated; composed of from ten to 

 twelve [obvious] segments. Abdomen nearly cylindrical, much 

 narrower than the cephalothorax and prolonged at the posterior 

 extremity into two more or less cylindrical caudal branches 

 [stylets]. First segment of thorax often anchyiosed with the head ; 

 fourth and fifth segments also often coalescent. Head only rarely 

 divided into two segments. Anterior antennae ver}* long and com- 

 posed of twenty-four or twenty-five joints; that of the right side in 

 the male often modified for grasping [geniculate]. Posterior 

 antennae large, composed of a basal joint, from which spring usually 

 two branches, the primary' branch consisting of two, the secondary 

 of several joints. Mandibles strongly toothed at the apex, palp 

 (usually) two-branched. Maxillae strong, and provided with a 

 many-lobed palp. Foot-jaws strongly developed: first pair very 

 broad; the basal joints having on the inner margin wart-like pro- 

 cesses, from which spring long ciliated bristles; the distal extremity 

 divided into three short joints which are thickly beset with strong 



