The specimen here described is an adult male. The peræon (Plate I, Fig. 1) is robust and covered with many blunt tubercles. In this respect it varies from the specimens described by others who say the peræon is smooth. The young are comparatively smooth and develop tubercles on the caudal segments first. Cephalon furnished with a sharp anteriorly directed dorsal tooth. First segment shorter than the second, which is triangular in shape; third and fourth broad and a little shorter than the second; fifth, sixth and seventh each growing smaller respectively and truncate at the tip. Antennæ, stout; superior pair not half as long as the body, first joint short and twice as thick as the second but only half as long, third joint shorter than first; flagellum as long as the peduncle and composed of 15 or 16 joints, inferior pair extending to about the middle of the flagellum of the superior, joints long and narrow. First gnathopod (Fig. 2), attached far forward, convex in shape and tapering slightly toward the finger, which was long as the palm and narrow; palm armed with tooth-like spine at the base and many hairs. Second gnathopod (Fig. 3), attached just posterior to the middle of the second pereiod, basal joint short and thick, not half as long as the palm; inner margin of the hand concave, armed with a tooth on the dorsal lobe and a broad, truncate tooth near the base of the finger, as well as numerous hairs; finger sharply concave on the inner margin for about half its length. Branchia nearly round. Third, fourth and fifth peræopods (Fig. 4) similar in structure, short, stout, and armed with stiff hairs; hand nearly as long as rest of the extremity; palm broad and armed with numerous hairs, inner margin slightly concave, with two serrate teeth at the base. Length of specimen, 13 mm. Color varying from a bright red to white. Several specimens taken at Laguna Beach the latter part of July, from the Rhodophyceæ on the rocks.