596 



BULLETIN 54, UNITED STATES NATIONAL MUSEUM. 



The first two segments of the abdomen scarcely shorter than the 

 other segments; the epimera of the third, fourth, and fifth segments 

 strong, subtetragonal. 



The terminal abdominal segment is triangular, short, hardly twice 

 as wide as long, rather convex above. 



The basal article of the uropoda is very wide, depressed; the outer 

 branch is carinated, with the apex rounded; the inner branch is inserted 

 at the inner angle of the basal article. Color grayish, pale on the 

 sides. Length, 8.5 mm.; width, 5 mm.; height, 2 mm. a 



ALLONISCUS PERCONVEXUS Dana. 



Alloniscus perconvexus DANA, Proc. Acad. Nat. Sci. Phila., VII, 1854, p. 176. 

 STIMPSON, Boat. Jour. Nat. Hist., VI, 1857, p. 506. BUDDE-LUND, Crust. 

 Isop. Terrestria, 1885, p. 225. UNDERWOOD, Bull. 111. State Lab. Nat. Hist., 

 II, 1886, p. 360. RICHARDSON, Proc. U. S. Nat. Mus., 

 XXI, 1899, p. 864; Ann. Mag. Nat. Hist. (7), IV, 1899, 

 p. 332; American Naturalist, XXXLV, 1900, p. 305. 



Localities. California; Pacific Grove; Santa Bar- 

 bara; Monterey Bay; Tillamook Head, Oregon. 

 Dug at mean-tide mark from sandy shore. 



Body ovate, very convex, not quite twice as long 

 as broad, 9 mm. : 16 mm. 



Head twice as wide as long, 2 mm.: 4 mm., with 

 the antero-lateral angles produced on either side into 

 an acute process, " horn-like," situated just in front 

 of the eye, and the front produced in the middle in 

 a large, widely rounded median lobe, extending as 

 far as the lateral process. The eyes are small, 

 oblong, composite, and situated in the antero-lateral 

 angles of the head close to the lateral margins. The 

 first pair of antennae are rudimentary and inconspicuous. They are 

 composed of three small articles. The second pair of antennas have 



a The above description is adapted from the following one of Budde-Lund' s : 



Breviter ovalis, subconvexus, obscure sed dense squamatus et punctis setigeris 

 crebratus. Antennae exteriores corpore dimidio breviores (7:17); flagellum scapi 

 articulo quinto brevius; flagelli articnlus secundus brevissimus, primus tertio sequalis. 



Processus frontales laterales majores, angustiores, prominentes, subconici; frons 

 media valde tumosa. 



Trunci annuli tres priores jnargine posteriore utrinque leviter sinuato; annuli 

 sequentes omnes margine posteriore medio post magis sinuato. 



Caudse annuli duo priores ceteris annulis vix breviores; epimera annuli 3-4-5 

 valida, subtetragona. Annulus analis, triangulus, brevis, segre duplo latior qtiam 

 longior, supra convexiusculus. 



Articulus basalis pedum analium perlatus, depressus; extus carinatus, apice rotun- 

 dato ; ram us interior angulo interior! articuli basalis insertus. 



Color griseus, in lateribus dilutior. 



Longitude, 8.5 mm.; latitude, 5 mm.; altitude. 2 mm. BUDDE-LUND, Crust. Isop. 

 Terrestria, 1885, pp. 228-229. 



FIG. 652. ALLONISCUS 

 PERCONVEXUS. 



