220 THE VOYAGE OF H.M.S. CHALLENGER. 



Remarks. — This is another robust species with a considerable resemblance to Antedon 

 Jlexilis (PI. XLII.) in its triangular arm-joints, expanded genital pinnules, and the 

 smooth, stout cirri arranged in ten vertical rows. But the centro-dorsal is somewhat 

 more conical than in that type and conceals the first radials entirely. The radial portions 

 of its margin are very deeply incised, so that its interradial angles are extremely 

 prominent, and they separate the lower lateral angles of the second radials, not of the 

 first, as in Antedon Jlexilis. In a side view of the calyx the second radials have an 

 almost V-shaped appearance, and are sometimes entirely invisible, owing to the manner 

 in which the axillaries project backwards into them. This gives a somewhat pear-shaped 

 appearance to the axillaries when seen " full," almost the whole of their length being 

 behind the line which joins their lateral angles. 



Antedon patula also differs from Antedon jlexilis in the characters of the lower arm- 

 joints. In the latter type they are smooth and rounded and in no way specially 

 prominent (PI. XLII.). But in Antedon patula the distal edges of the fourth and each 

 of the following brachials, till the twenty-fifth or thirtieth, are raised into a sort of collar, 

 which stands up above the base of the next joint ; and as soon as the joints assume a 

 triangular shape they are marked by a distinct medio-dorsal ridge, which gives the arm 

 a carinate appearance, a character which is altogether absent in Antedon Jlexilis. The 

 joints of the genital pinnules are also somewhat carinate, and less enlarged than in 

 Antedon Jlexilis ; but there is the same plating over the genital glands as in that species, 

 though the sacculi are not quite so abundant. 



6. Antedon robusta, n. sp. (PI. XLIV. fig. 1). 



c 

 Specific formula — A. 2.^. 



Description of an Individual. — Centro-dorsal a thick disk, 9 mm. wide, and bearing 



about fifty cirri round its margin. These have from eighteen to twenty-three smooth, 

 stout joints, several of which are longer than wide. The penultimate forms a small 

 opposing spine. 



First radials just visible at the angles of the calyx above the low interradial 

 processes of the centro-dorsal, which partly conceal the short second radials in their 

 median line. Axillaries widely rhombic, with an open distal and sharper proximal 

 angle, the latter rising to form a prominence with the second radial. Twelve arms, 

 there .being one bidistichate series on each of two rays. The first two brachials (or the 

 distichals when present) form a slight prominence as the outer radials do, and have 

 much flattened outer sides like the axillaries. The inner sides of the second, and both 

 sides of the third brachials, are also sometimes flattened. Arms long, of more than two 

 hundred smooth joints, the first few oblong, and the later joints more triangular. A 



