3l8 * CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



Suborder ISOPODA. 



Family LIGIID^. 



Styloniscus gracilis Dana. 

 Plate XXXVI, Figs. 29-31. 



Styloniscus gracilis Dana, Proc. Acad, Nat. Sci. Phila. v. 7, p. 176, 1854. 

 Stimpson, Jour. Bost. Soc. Nat. Hist. v. 7, p. 506, 1857. Stuxberg, 

 Ofversigt af k. Vetensk. Akad. Fbrhandl. 1875, N:o 2, p. 43. Budde- 

 Lund, Crust. Isop. Terrestria, p. 271, 1885. Richardson, Proc. U. S. 

 Nat, Mus. V. 21, p. 867, 1899. 



Alloniscus maculosus Harford, Proc. Calif. Acad. Sci. v. 7, p. 54, 1877. 



Thoracic segments smooth, glossy, and of subequal length; postero- 

 lateral and antero-lateral angles of the first 4 rounded, the postero-lateral 

 angles of the last 3 segments acute and produced backwards. 



Abdomen longer than wide, abruptly narrower than the thorax, the first 

 2 segments shorter than the others, the 3 following segments with the 

 postero-lateral angles acute and produced backwards. Terminal segment 

 twice as wide as long and very broadly rounded. 



Head transverse, devoid of prominences, front broadly rounded. Eyes 

 rather large reaching the lateral margins of the head. Antennules three- 

 jointed, not exceeding the second basal joint of the antennae; first joint 

 broad, distally widened; second joint subcylindrical, slightly longer and 

 much narrower than the first; third joint very minute and joined to one 

 corner of the preceding. Antennae nearly \ the length of the body, first joint 

 short, transverse, second and third joints oblong, cylindrical, subequal, 

 fourth joint as long as the 3 preceding, fifth joint narrower and slightly longer 

 than the fourth; flagellum about as long as the 2 preceding joints and com- 

 posed of 13-15 articulations. 



Mandibles short and very stout, having a large molar tubercle and a 

 narrow dark-colored, dentate cutting edge, but no palp. First maxillae with 

 the inner plate short and furnished with 3 short-ciliated setae, the upper i 

 much shorter than the lower 2 which are of subequal length; outer plate 

 narrow and armed with 5 curved teeth. Second maxillae narrow, with 2 

 very small ciliated plates on the inner margin near the rounded tip. Inner 

 plate of the maxillipeds with several short, densely ciliated processes on the 

 transverse distal margin and a large ciliated seta on the inner side; palp five- 

 jointed, the terminal joint minute. 



Legs very spiny below; dactyls short, furnished with several setae and i 

 or 2 spines below near the tip. Uropods slender, fully \ the length of the 

 abdomen; peduncle oblong, flattened, the inner angle strongly produced 

 backwards; rami slender, microscopically scabrous but devoid of spines; 

 inner ramus exceeding the outer in length but slightly more slender, the 

 tip furnished with setae. 



The body is furnished with scattered fine short hairs which are more 

 conspicuous on the posterior margins of the segments. 



Length ^-^ inch. 



