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



simple and the side arm plates lie on the nnder surface and bear several rough, cylindrical 

 tentacle scales (or arm spines). These plates are continued upward by a doul:)le row of 

 large grains, homologous with upper arm plates, which bear minute hooks. Two small 

 genital openings in each iuterbrachial space at the outer corners. 



This genus differs outwardly from Astrogomjihus chiefly in having no spikes on the 

 disk, and in having disk scales of a different character. 



Species of Astrochele not herein described. 



Astrochele lymani, VIL, Am. Journ. Scien., vol. xvi. p. 374, 1878. 

 N.E. Coast of North America; 200-980 fathoms. 



Astrotoma. 



Astrotoma, Lym., IlL Cat. Miis. Comp. Zool., No. viii. part 2, 1875. 



Disk arched and traversed above by ten low radiating ridges formed by the radial 

 shields, and closely granulated. There are no mouth papUlte, and the spiniform teeth 

 and tooth papillae form an ii-regular clump at the apex of the mouth angle, somewhat as 

 in Astropliyton. The arms are simple and the side arm plates are confined to then- lower 

 surface, and bear several pegdike scarcely rough, tentacle scales (or arm spines). These 

 plates are continued upwards by a double row of granules bearing minute hooks which 

 are encased in thick skin bags. The annular ridges thus formed are wide and rather 

 indistinct. Two small genital openings in each interbrachial space, at the outer corners. 



Astrotoma agassizii, Lym., lU. Cat. Mus. Comp. Zool., No. viii., part 2, p. 24, pi. iv. 

 figs. 57, 58, 1875. 



Straits of Magellan ; 135 fathoms. 



Astrotoma murrayi, Lym. (PL XXIL figs. 5-7). 



Astrotoma Muiray!, Lym., Bull. Mus. Comp. ZooL, vol. vi., pt. 2, p. 61, pi. sviii. figs. 474-476, 

 1879. 



Large tubercles, or smooth warts, on the upper side of disk. No booklets on belts of 

 grains onarms, except close to their tip. Clustersof grains ininterbrachialspacesnextmouth. 



(Type specimen from Station 194.) Diameter of disk 29 mm. Length of arm 

 280 mm. Width of arm near disk 7 mm. Height of arm near disk 7 mm. Apex of 

 mouth angle, embracing all the region of the jaw plate, densely set with short, sharp, 

 nearly equal, spine-like papUlse, thirty or more in number, and arranged in transverse 

 rows of three or four. Lower surface and a part of the sides of the protuberant mouth 

 angles closely set with rounded and sometimes elongated grains. One round madreporic 

 mouth shield, 1"5 mm. in diameter, lying on the margin of the horizontal mouth region, 

 where it is separated from the vertical interbrachial space by a fold of skin stretched 

 between the bases of the arms. Arms high, and tapering gradually to their tips, covered 



