REPORT ON THE CRINOIDEA. 127 



outer sides, which are enlarged at the expense of the inner sides (PI. XXI. fig. 2 ; fig. 3 

 on p. 122). But the expansion of the pinnule-joints is much more uniform in Antedon 

 tuberosa, as they increase and then decrease gradually from the base to the end of the 

 pinnule, while both sides of each joint are enlarged, though the outer is slightly more so 

 than the inner one. In these characters Antedon tuberosa resembles the smoother 

 Antedon parvipinna and the ten-armed variety of Antedon fiexilis ; but apart from its 

 occasional bidistichate character (PL XLIL), the latter form is readily distinguished by 

 its longer cirri, the appearance of the first radials externally, and by the smoothness of 

 the arm-bases. 



All three species are remarkable for the great development of the sacculi, which are 

 found not only between the side plates of the distal pinnules, but also along the medio- 

 ventral line of the plated genital pinnules as in Antedon incisa (PL XXI. fig. 2a) ; but 

 they are often absent in this position in other species, as, for example, Antedon acosla 

 (see Part I. pi. liv. figs. 1-3). 



A young larva was obtained at Station 210, which must belong either to Antedon 

 tuberosa or to Antedon distincta (PL LI. fig. 1), the only two species found at this station. 

 The latter, however, is a multibrachiate form with both distichal and palmar series, and 

 from the appearance of the larva I think that it should most probably be referred to 

 Antedon tuberosa. It is represented in PL XIV. fig. 9, and is so very similar to the 

 corresponding stage of the Pentacrinoid of Antedon rosacea, except perhaps for being a 

 trifle more robust, that little need be said about it. The centro-dorsal is still small and 

 without any indication of its subsequent enlargement for the development of cirri, and 

 but very few arm -joints have appeared above the radial axillaries. 



16. Antedon parvipinna, n. sp. (PL XV. fig. 9). 



Specific formula — A.—. 



Description of an Individual. — Centro-dorsal discoidal, bearing some fifteen marginal 

 cirri. These have about fifteen stout joints, of which the fifth and sixth are slightly 

 longer than wide. 



Minute plates, probably the basal rays, rest upon the interradial angles of the centro- 

 dorsal and separate the bases of the nearly oblong second radials, the outer parts of 

 which are in close lateral contact. Axillaries short and wide with very open angles, and 

 also in close apposition. Both these joints have traces of a median keel which is 

 continued on to the arm-bases. The first brachials nearly oblong, with their outer sides 

 flattened ; the inner sides of the second and hypozygals of the third brachials also flattened. 



Ten arms ; the joints after the eighth triangular, at first considerably shorter than 

 wide, but gradually becoming more nearly equilateral and finally quadrate. A syzygy in 



