ISOPODS OF NORTH AMERICA. 59 



Found in soft clay with great stones; soft, black-grayish clay. 



"Male: Body rather elongated, with the mesosome of nearly uni- 

 form breadth throughout, and the median constriction not very much 

 pronounced. Cephalosome of moderate size, rounded quadrangular, 

 with the supraocular processes well denned. Dorsal face of both 

 cephalosome and mesosome very uneven, with irregular depressions, 

 and clothed all over with minute spinules and short hairs. Penulti- 

 mate pedigerqus segment divided dorsally by a narrow longitudinal 

 groove into two halves. Metasome comparatively narrowband scarcely 

 longer than the two posterior pedigerous segments combined; epimera 

 small. Eyes well developed, though not very large. Mandibles com- 

 paratively small, with only a very slight notch outside; inner edge 

 obtusely produced in the middle, tip acute, slightly incurved. Perio- 

 poda with small tubercles inside the outer joints. Terminal segment 

 of metasome considerably narrowed in its outer part, which is conical 

 in shape. Uropoda with the rami comparatively narrow. Female: 

 Body much broader than in male, with the last three pedigerous seg- 

 ments well-defined, and together forming an oblong oval division 

 about three times as long as that preceding it. Cephalosome with the 

 frontal part slightly produced and bidentate at the tip. Pleopoda in 

 both sexes with the rami quite smooth, forming narrow sac-like plates 

 not fitted for swimming but apparently respiratory in character. 

 Color of male gra\ T ish white, with a light bluish tinge; of female, 

 yellowish, semipellucid, with scattered brown dots. Length in both 

 sexes, 4 mm." G. O. SARS. a 



Ohlin 6 also describes the color of the male as grayish white, that of 

 the female wax-like yellow, and that of the larvae yellowish-white or 

 nearly white. The eyes are in all red-brownish. 



Sars states that the adult animal is very sluggish in habit, the struc- 

 ture of the pleopoda showing it to be quite unable to swim. The 

 larvae, on the other hand, move through the water with great agility, 

 and most probably at times lead a parasitic life on the skin of various 

 fishes. 



GNATHIA CERINA ( Stimpson ) . e 



Praniza cerina STIMPSON, Smithsonian Contributions to Knowledge, VI, 1853, 



p. 42, pi. m, fig. 31. 

 Anceus americanus STIMPSON, Smithsonian Contributions to Knowledge, VI, 1853, 



p. 42. 

 Praniza cerina VERRILL, Am. Jour. Sci. (3), VI, 1873, p. 439; VII, 1874, pp. 



38, 41, 411, 502; Proc. Am. Assoc., 1873, pp. 350, 354, 358, 362 (1874). 

 Gnalhia cerina HARGER, Proc. U. S. Nat. Mus., II, 1879, p. 162; Report U. S. 



Commissioner of Fish and Fisheries, 1880, Pt. 6, pp. 410-413, pi. xn, figs. 



75-79. RICHARDSON, American Naturalist, XXXIV, 1900, p. 214; Proc. 



U. S. Nat. Mus., XXIII, 1901, p. 507. 



Crust, of Norway, II, 1899, p. 55. 



&Bihangtill K. Sv. Vet.-Akad. Handl., XXVI, Afd. iv, No. 12, 1901, pp. 20-21. 



c See Harger for excellent description of male, female, and larva. 



