[From the Americak Journal op Science and Arts. Vol. XI, April, IS76. ] 



Description of Mancasellus brachyui'us, a new fresh water Isopod ; 

 by O. Harger. 



The genus Asellopsis"^ was proposed by the writer for the 

 reception of Asellus tenax Smith, on account of the absence of 

 mandibular palpi. A second species of this interesting genus 

 has lately been collected by Mr. Fred. Mather, in Kockbridge 

 Co., Virginia. Since the name Asellopsis proves to have been 

 preoccupied I propose in its place Mancasellus^^ retaining M. 

 tenax as the typical species, while the new species may be called 

 M. brachyurus, from the short caudal stylets. This species re- 

 sembles M. tenax, described and figured in the Keport of the 

 United States Commissioner of Fish and Fisheries, Part II, 

 Eeport for 1872-3, p. 659, plate I, fig. 3, differing principally 

 from it in the following points : The lateral margins of tbe head 

 are entire; the proximal segment of the caudal stylets is short, 

 being but little longer than the third segment of "the antennae ; 

 the rami are also short, the inner being much stronger and 

 somewhat longer than the outer; in the males the propodus of 

 the first pair of legs is armed with a prominent acute tooth on 

 the palmar margin near the base, and, in the appendages of the 

 seventh segment, the terminal portion of the outer pair is 

 smaller and less expanded externally than in M. tenax, and the 

 distal segment of the internal ramus of the inner pair is but 

 little swollen at the base, and approaches the form seen in Asel- 

 lus communis Say. The largest specimen measures 16™™. m 

 length exclusive of the antennse and caudal stylets. The local- 

 ity is worthy of mention as being on the Atlantic side of the 

 Appalachian water-shed while J/, tenax is yet known only from 

 the Lakes. 



* This Journal, III, vol. vii, p. 601, 1874. 

 f From manciis, maimed, and Asellus. 



