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Show 690 MESSRS. BRADY AND ROBERTSON ON [Nov. 21, It will be observed that though the two birds are nearly the same in linear dimensions, A. ncevioides is a heavier and more robust bird ; its beak is larger and more massive, and its tarsi, toes, and claws are longer. 3. Descriptions of two new Species of British Holothuroidea. By GEORGE STEWARDSON BRADY, C.M.Z.S., and DAVID ROBERTSON, F.G.S. [Eeceived October 27, 1871.] (Plates LXXI. & LXXII.) SYNAPTA TENERA, Norman. (Plate LXXI. figs. 1-4.) Body about eight times as long as broad, tapering slightly towards the posterior extremity: tentacles short and sparingly pinnate. Anchor-plates few in number, subpentagonal, with a broad handle or pedicle, the length of which is equal to about one half the width of the plate: one broadly ovate, crenulated, central perforation, surrounded by five of similar size and shape and another crescenti-form, the last named being situate just above the base of the pedicle. The pedicle itself has near its base a wedge-shaped aperture, and at the free extremity two or three irregular sublinear perforations. The anchors themselves are slightly longer than the anchor-plates, and are often minutely and irregularly perforated in the shaft and arms. At the bases of the tentacles are a few minute spicules, curvilinear in form, with divaricated furcate extremities (fig. 4). The whole animal is very tender and delicate in structure, and almost perfectly transparent, five opaque white longitudinal lines, however, being very conspicuous. Length an inch to an inch and a half. The only locality in which we have met with this species is the Frith of Clyde, where it occurs not unfrequently in black ooze, in a depth of 15-30 fathoms. Synapta tenera was named and briefly referred to by the Rev. A. M . Norman at a meeting of the British Association some few years ago, his remarks being based upon specimens taken by Mr. Robertson in the above-mentioned locality. CUCUMARIA SAXICOLA, nov. sp. (Plate LXXII.) Body of nearly equal thickness throughout, scarcely at all tapering at the extremities ; skin excessively thick and strong. The spicules of the body are usually subrhomboidal in shape (fig. 3 a), but in process of growth tend to lengthen out at the extremities (fig. 3b); each plate has in the centre four oval perforations arranged diamond-wise, the two in the short axis being the largest; but as the plate increases in size more perforations become developed in the direction of the long axis (b). These plates are by no means very thickly set and are interspersed with numerous much smaller spicules of a stel- |