416 BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



sixth thoracic segment, when retracted. The maxilliped has a palp of 



five articles. The palp of the mandibles is wanting. 

 The segments of the thorax are subequal with lateral margins entire. 



The epimera are not separated from the segments, being entirely 



coalesced, with no indication of 

 a separation. 



The abdomen consists of two 

 short segments followed by a 

 large terminal one, rounded 

 posteriorly. There is no lobe 

 on the posterior margin be- 

 tween the uropoda. The uro- 

 poda are shorter than the ter- 

 minal abdominal segment. The 

 length of the terminal abdomi- 

 " nal segment is 3 mm. The 



FIG. 467. MAXCASELLVS TENAX. a, ABDOMEN WITH , , i ,. , i j , 



VROPODA. X 11*. 6, FIE8T LEG. X 20*. l6n th f th6 UTOpoda IS '2 111111. 



The peduncle of the uropoda is 



1 mm. The inner branch is as long as the peduncle, being 1 mm. long. 

 The outer branch is half as long as the inner branch. 



The first pair of legs are subchelate. The propodus has a single 

 triangular expansion on the inferior side. There are numerous spines 

 on the inferior margin of the propodus and dactylus. All the other 

 pairs of legs are ambulatory with dactyli bi-unguiculate. 



MANCASELLUS TENAX DILATA Smith. 



Mancasellus tenax dilala SMITH, Report U. S. Commissioner of Fish and Fisheries, 

 1874, p. 661. 



Locality. Detroit River. 



"The flagellum of the antennula? contains one or two more segments 

 [than in the preceding species]. The lateral portions of the head and 

 segments of the body, especially in fully adult specimens, are expanded 

 so that the outline of the animal is a broader oval. The open sinus in 

 the lateral margin of the head is a narrow incision, rounded at the bot- 

 tom, but with the sides sometimes meeting. The propodus in the first 

 pair of legs is nearly as much enlarged in the males as in A. communis, 

 and is armed on its palmary margin with three acute teeth, of which 

 the middle one is the largest." SMITH. 



MANCASELLUS LINEATUS (Say). 

 Asellus lineatus SAY, Jour. Acad. Nat. Sci. Phila., I, 1818, p. 428. DE KAY, Nat. 



Hist. New York, Pt. 6, 1844, p. 50. UNDERWOOD, Bull. 111. State Lab. Nat. 



Hist., II, 1886, p. 359. 

 Mancasellus lineatus RICHARDSON, American Naturalist, XXXIV, 1900, p. 297; 



Proc. U. S. Nat. Mus., XXIII, 1901, p. 551. 



Locality. South Carolina. 



"Body oblong; interior antennae much shorter than the peduncle of 

 the exteriors; caudal appendices, peduncle cylindrical. 



