This species is separated from _E. uncinatus_ (Philippi) with some hesitation since specimens of the latter are not at hand for direct comparison. It would seem, however, to be clearly different, to judge from Ehler's figure, in the form of the uncini. These are much broader (i.e., at right angles to the dental line), the base projecting conspicuously but not forming an angulate shoulder as in _E. gracilis_, being nearly evenly and rather broadly rounded. The teeth are mostly seven in number, the end below the last of these set off as usual, rounded. The upper collar setæ coarse, with two teeth or spurs at base of the slender tip, these commonly more or less unequal in size. Branchiæ thirteen pairs. Operculum in general as in _uncinatus_; width of principal expansion 1.25 mm.; the latter even, by narrowing into the stalk, the rim with thirty-eight projecting acute teeth or serrations which are straight or very nearly so, not at all uncate as in uncinatus in which they are also fewer (thirty). Inner crown of eleven spines each tapered evenly to an acute tip and bent in abruptly toward the center above, the proximal portion being erect and ordinarily parallel with the others. No process or series of processes detected within this crown, the base from which these arise being evenly concave on its distal surface and convex on the proximal. Spines of the inner crown dark brown proximally as is the entire basal plate from which they arise, the remaining part of spines light brown. Operculum proper nearly black below teeth on proximal surface of the expansion and on adjacent part of stalk the remaining part of which is white; distal surface of funnel pale. Branchiæ and body in general pale, unmarked or some of the branchiæ with a blackish mark on stalk toward distal end. Thoracic setigerous somites seven. Abdominal segments, ninety. Type--M. C. Z. 2, 178. Length exclusive of branchiæ, 20 mm.; to end of operculum, about 24 mm. Width, 1.5 mm. The Nervous System of Cæcum Californicum WILLIAM A. HILTON (_Contribution from the Zoological Laboratory of Pomona College_) Specimens of this little gastropod mollusc from 2 to 3 mm. in length were the material for the study. Specimens were fixed and sectioned whole and a few good series were obtained. It seems rather remarkable that so small a species should have such a high organization of the nervous system. The ganglia are large in proportion to the size of the animal and well developed. In all cases the exact limits of the nerves and connectives were not determined, but the chief ganglia were easily found.