420 BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



c. Epiraera present on the first segment of the thorax only. Head with the lat- 

 eral margins produced in a lobe on either side. First pair of antenna", with 

 a flagellum of twelve articles, extend to the middle of the fifth article of the 

 peduncle of the second antennae. Second pair of antennae extend to the 

 posterior margin of the fifth thoracic segment. Inner branch of the uro- 

 poda is as long as the peduncle. Uropoda one-fourth of a millimeter longer 

 than half the length of the terminal segment of body. 



Asellus brevicauda Forbes 



e 7 . Epimera not evident on any of the segments of the thorax. Head with the 

 lateral margins not produced in a lobe on either side. First pair of antenna', 

 with a flagellum of seven articles, extend almost to the end of the fourth 

 article of the peduncle of the second antennae. Second pair of antennae 

 extend to the posterior margin of the seventh thoracic segment. Inner 

 branch of uropoda is twice as long as peduncle. Uropoda one-third of a 

 millimeter shorter than half the length of the terminal segment of the 



body Asellus hoppinsc Faxon 



a'. Propodus of first pair of legs not armed with two triangular processes. 

 b. Propodus of first pair of legs furnished with few spines. 



c. Second pair of antennae as long as the body. Propodus of first pair of legs 

 elliptical in outline and armed with one long spine. Terminal segment of 



body with median lobe small Asellus attenuatus Richardson 



</. Second pair of antennae extend to the posterior margin of the fifth thoracic 

 segment. Propodus of first pair of legs produced in the male on the infe- 

 rior margin in a roundly triangulate expansion furnished with three long 

 spines. Terminal segment of body with median lobe large and conspicu- 

 ous Aselhts aquaticus (Linnaeus) 



b'. Propodus of first pair of legs furnished with numerous short spines or stiff 

 hairs Asellus tomalensis Harford 



ASELLUS COMMUNIS Say. 



Asellus communis SAY, Jour. Acad. Nat. Sci. Phila., I, 1818, pp. 427-428. 



Asellus rulgaris GOCLD, Invertebrata of Massachusetts, 1841, p. 337. 



Asellus communis DE KAY, Nat. Hist. New 7 York, Pt. 6, 1844, p. 49. SMITH, Report 



U. S. Commissioner of Fish and Fisheries, 1874, Pt. 2, p. 657, pi. i, fig. 4. 

 Asellus militaris HAY, Bull. 111. State Lab. Nat. Hist., No. 2, 1878, p. 90. 

 Asellus communis HAY, American Naturalist, XVI, 1882, p. 241. UNDERWOOD, 



Bull. 111. State Lab. Nat. Hist., II, 1886, p. 358. RICHARDSON-, American 



Naturalist, XXXIV, 1900, p. 297; Proc. U. S. Nat. Mus., XXIII, 1901, p. 



551. PAULMIER, Bull. New York State Museum, 1905, p. 178. 



Localities. Schuylkill River, Pennsylvania; Connecticut; Massa- 

 chusetts; New York; Indiana; Illinois; Michigan; Mississippi; San- 

 dusky, Ohio (E. L. Moseley); Cincinnati, Ohio; Rhode Island; edge 

 of Potomac River, Virginia side. 



Body oblong-ovate, three times longer than wide, 5 mm. : 15 mm. 

 Sides of body almost parallel. 



Head twice as wide as long, 1^ mm. : 3 mm. , with the anterior mar- 

 gin excavate. The head is narrower anteriorly than posteriorly, being 

 only 2 mm. wide in front. The eyes are small, round, composite, and 

 situated at the sides of the head, halfway between the anterior and the 

 posterior margins. The first pair of antennae have the basal articles 



