1854.] 3 



it shall be to take such steps as they may deem expedient to recommend 

 to the Government the scientific exploration of Africa. 



Committee, Dr. Ruschenberger, Dr. Leidy, Mr. Lea ; Prof. Carson 

 and Dr. Hallowell. 



Junuary 31 si. 

 Vice-President Bridges in the Chair. 

 The Committees to which were referred the following papers, severally 

 reported in favor of their publication in the Proceedings : 



On a new Entomostracan, of the family LimnadidjE, inhabiting the Western 



waters. 



By Charles Girard. 



LIMNADELLA, n. g. 



Gen. Char. Eye one. Antennae subequal, provided upon their inferior side 

 with long and plumose setae, whilst on the upper side there are short, slender 

 and simple spines. Two elongated tape-shaped jaws. Eeet in twenty-lour 

 pairs, provided upon their extremities and sides with slender and plumose setae, 

 or hairs. A series of spiny processes along the posterior half of the dorsal line. 

 Post abdominal plate very large. Nutritive system phlebenteric. 



Observations. This genus diners from Limnadia in being provided with one 

 eye only, instead of two. Also by its antennae, the two pairs of which are 

 similar in structure, whilst in Limnadia one pair is smaller than the other. The 

 post abdominal plate and number of feet will afford other distinguishing charac- 

 ters between Limnadella and Limnadia. From Cyzicus or Estheria it differs, 

 first, by the structure of the shell, which in Estheria resembles that of an Area, 

 whilst, in Limnadella, it is altogether Cyproid in its general aspect. There 

 is a marked difference between these two types in the structure of the an- 

 tennae, the joints of which are provided on their upper part with numerous spines 

 in Limnadella, whilst in Cyzicus there is but one single spine at the anterior 

 edge. The structure of the feet is likewise dissimilar, being furnished with 

 plumose setae in Limnadella. 



Limnadella Kitet, n. sp. 



Spec. Char. Shell : elongated, subelliptical, thickest anteriorly ; twice as 

 long as deep ; anterior, inferior, and posterior margins regularly continuous ; 

 upper outline somewhat irregular on account of the beaks being rather promi- 

 nent. Valves uniformly convex. Greatest depth one eight of an inch, greatest 

 length one quarter of an inch. Specimens may occasionally attain to a larger 

 size. Color, deep or light brown, mottled with black. Animal : antennae 

 composed each of twelve or thirteen subequal joints. Twenty-four pairs of 

 feet, the six posterior ones diminishing gradually away so as to render the last 

 three rudimentary. The last of all is inserted upon the last caudal segment but 

 one. There is a broad sub-triangular plate, terminated by two pairs of very large 

 spines, curved upwards; the inferior pair being longer and slenderer than the up- 

 per one. The concave margin of that plate is furnished with a series of quite 

 small spines. On the uppermost part of the post-abdominal plate is inserted a 

 pair of very delicate sword shaped appendages, very difficult to be observed 

 even with a good microscope. Along the posterior half of the back there exists 

 a series of sixteen processes, provided upon their upper and posterior sides with 

 about five or six minute curved spines, the tip of which is bent backwards. 

 The anterior two of these processes are but rudimentary ; the most developed 

 occupy the middle of the series; the posterior ones again diminish gradually as 

 they approximate the post-abdominal plate. 



Specimens collected at Cincinnati were sent to the Smithsonian Institution by 

 Thomas Kite, of that city. 



