ASTROTOMA AGASSIZII. 25 



joints by annular ridges of granules bearing microscopic spines. Close to 

 the tip of the arm, each joint has a ridge of two annular rows of grains 

 {Fig. 56), and each grain carries a microscopic spine. These two rows of 

 spines interlock like the teeth of saws, and are folded flat to the arm. Be- 

 tween the ridges are depressions which are covered by three annular rows 

 of gi'ains. The madreporic plate lies in the mouth region inside the line of 

 coarse grains connecting the bases of the arms ; it is oval and surrounded by 

 a setting of coarse granules. Disk roughly circular, with ten slightly re-en- 

 tering curves at the bi'achial and interbrachial margins. Radial ribs feebly 

 marked and rimning quite to the centre ; they are more coarsely granulated 

 than the rest of the upper surface (whose granulation makes a sort of net- 

 work pattern), and have four or five grains in the length of a mm. Inter- 

 brachial spaces below distinguished from the mouth region by their smoothness 

 and their minute granulation. Tentacle-spines short, stout, blunt, slightly 

 flattened, standing erect ; there are none by the first pore, two by the 

 second, and three or four by those beyond ; their bases are surrounded by a 

 little ridge of granulation, outside which is the pore through which protrudes 

 the small, short, smooth tentacle {Fig. 54). Close to the tip of the arm there 

 are two spines to each pore ; and here they are comparatively mvich larger, 

 are covered with skin and hooked at the end ; at their base are two micro- 

 scopic spines similar to those on the ridges of the arm {Fig. 56). The very 

 tip of the arm is divided into joints, but, as yet, has no grains or minute 

 spines ; there is, however, a stout curved tentacle-spine to each pore {Fig. 55). 

 The genital openings are short, and lie at the outer corners of the inter- 

 brachial spaces. 



Color, in alcohol, nearly white. 



Hassler Expedition ; Straits of Magellan, at the junction of Smythe's Chan- 

 nel, on the Pacific side ; one specimen from 135 fathoms. 



