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



7. Antedon compressa, n. sp. (PI. XLL). 

 Specific formula — A. 2.^. 



Centro-dorsal a thick convex plate, with the dorsal pole free, and fifteen to twenty 

 marginal cirri. These have about twenty joints, a few of which are longer than wide, 

 and the later joints are somewhat compressed laterally, with blunt dorsal spines. 



The first radials are concealed, and sometimes also parts of the second. These are short 

 and sharply convex, with a slight median ridge, and they meet one another laterally 

 beyond the angles of the centro-dorsal. Axillaries short and widely rhombic, also with a 

 median ridge, and forming a small tubercle with the preceding joints. The rays divide 

 twice ; distichals two, with a faint median ridge, the axillaries without a syzygy, short 

 and widely rhombic. The outer sides of the radial axillaries, distichals, and of the two 

 lower brachials are slightly flattened ; and the inner sides of the second and third 

 brachials are also somewhat flattened. 



Fifteen to twenty arms, of one hundred and fifty or more joints ; the lowest are 

 nearly oblong, with indications of a dorsal keel and raised distal edges. The following 

 joints more triangular and distinctly carinate, gradually becoming quadrate and somewhat 

 compressed laterally, with a tendency to overlap. A syzygy in the third, and then in 

 the eleventh or twelfth brachial ; others at intervals of two to seven, usually four or five 

 joints. 



The second brachial bears a tolerably stout pinnule some 10 mm. long, and consisting 

 of about eighteen short joints, the first few of which are much wider than their successors 

 and slightly prismatic. That of the third brachial is smaller, with the basal joints more 

 rounded, and not so wide ; and the following pinnules diminish in size till about the 

 tenth brachial, having fewer but relatively longer joints. Beyond this point the length 

 gradually increases again and the later pinnules are slender and delicate, with the two 

 basal joints flattened and somewhat expanded. 



The disk is well plated along the ambulacra ; but the interpalmar areas only have a 

 few scattered granules ; the brachial ambulacra and interarticular spaces also well plated. 

 The side plates of the pinnule-ambulacra are fairly distinct, with intervening sacculi. 



Colour in spirit, — very light brown ; the disk darker. 



Disk 8 mm.; spread 28 cm. 



Localities. — Station 192, September 26, 1874 ; near the Ki Islands ; lat. 5° 49' 15" S.; 

 long. 132° 14' 15" E.; 140 fathoms; blue mud. Two specimens. 



Station 201, October 26, 1874; Philippine Islands; lat. 7° 3' N., long. 121° 48' E.; 

 82 fathoms ; stones, gravel. One specimen. 



Remarks. — This species is in some respects a transitional form between Antedon 

 patula. and Antedon flexilis on the one hand, and the Palmata-gvou]) on the other. The 



