I have now to add another obtained from the same well as the other Subterranean Crustacea that I have described. Genus Phreatoicus, (novum). Body long; sub-cylindrical, laterally compressed. Upper antenna short, lower long, with flagellum. Mandible with an appendage. First pair of legs subchelate, others simple; first four pairs articulated to body at the anterior ends of their segments and directed forwards, last three articulated at posterior ends of their segments and directed backwards. Abdomen long, of six distinct segments, last joined to telson. Sixth pair of pleopoda biramous, styliform. Telson large, subconical. Phreatoicus typicus, sp. nov. Pl. IV. Eyes not visible. Upper antenna about half as long as the peduncle of the lower antenna, consisting of about eight joints, peduncle not distinguishable from the flagellum, last three or four joints thicker than the preceding. Lower antenna about three-fourths as long as the body, peduncle of five joints, first two short, third longer but not so long as the fourth, fifth nearly as long as the third and fourth together. First pair of legs subchelate, propodos rather small, palm oblique, defined by densely haired knob; finger strong, hairy; next three pairs of legs subequal, rather stout; last three longer, setose, increasing regularly in length from before backwards. First segment of pereion only about half as long as the second, remainder subequal. Pleon two-thirds as long as pereion, first segment small, next three subequal, fifth large, about as long as the preceding three together, the second, third, fourth and fifth segments having the integument produced inferiorly, and the inferior edge fringed with short stout setæ. Sixth segment joined to telson and bearing a pair of biramous pleopoda; peduncle longer than rami, outer ramus shorter than inner. Telson large, subconical, deeply concave below, inferior edge irregularly serrate and fringed with very short setæ; regularly rounded above, extremity projecting backwards, with short setæ on tip, and a stout one on each side of the base. Colour—transparent. Length, about half an inch. Hab. Pump at Eyreton. Additional remarks on structure:— The upper antenna (pl. IV., fig. 2) is peculiar in having the last three or four joints considerably thickened, the thickening being chiefly due to the increased thickness of the integument. Small simple auditory cilia are found on the under side of the antenna (fig. 2 a). The lower antenna (fig. 3) has already been sufficiently described.