28 ASTROPHYTOX POURTALESII. 



Astrophyton Pourtalesii Bp. qot. 

 PI. IV. f. 41 -4S. 



Special Mirks. — Disk round and fleshy, covered by a thick skin, through 

 which show numerous grains on the upper surface. Three or four tentacle- 

 spines to each pore, extending to within one or two pores of the mouth. 

 One madreporic body, often covered by the skin, and situated at the inner 

 angle of the interbrachial space. 



Description of an Individual. — Diameter of disk, 63 min \ Width of arm where 

 narrowest within the disk, 8"" n . Width of largest branch, outside disk, 8 mm -. 

 Total length of arm measured along its branches, 204 Bun- , to wit: 1st fork 

 (which is within the disk) to the 2d (which is outside), 16 mm - ; 2d to 3d, 

 32 : 3d to 4th, 30 nm ' ; 4th to 5th, 27 mm -; 5th to 6th, 2!) mm ; 6th to 7th. 

 27 mm ; 7th to 8th, lo mm - ; 8th to 9th, 10 n,m - ; 9th to 10th, 7 mm -; 10th to 11th, 

 7 mm •; 11th to end, 4 mm '. Mouth-papilla 1 , teeth, and tooth-papillae all similar 

 and spinilbnii ; small, nearly equal, and about a dozen to each mouth-angle. 

 Arms smooth, covered with thick skin, and rounded. The terminal twigs 

 have their joints marked by annular ridges | Fig. ;;). which hear a double row 

 of minute spines, folded down on the ridge, and alternating with one another. 

 Disk fleshy, nearly circular, and covered by a thick skin ; the radial ribs 

 slightly marked. There are neither spines nor stumps, but a quantity of 

 scattered granules, which are most plenty near the centre of the back, and 

 are almost wanting in the lower interbrachial spaces. At the inner angle of 

 one of the interbrachial spaces is the madreporic shield, which is so covered 

 by skin as to he hard to distinguish. Three or four tentacle-spines on all 

 the larger branches; short, blunt, spiniform, of equal size; about -""" long. 

 On the two pairs ofpores nearest the mouth, no spines, or only a single one: 

 the following three or four pores have two spines each ; and those beyond, 

 three or four. Each pore on the terminal twigs has hut two tentacle-spines, 

 in form of strong spinj -tump- covered with -Kin {Fig. ;■'.'/), close to which 

 the tentacle (g') protrudes. 



( lolor, in alcohol, nearly w hitc 



A larger specimen had the disk 7"»""" in diameter. The distances from one 



fork of the arm to the next were as follow-. Lsl to 2d, It : 2d to 3d, 



3d to iih. 27 : 1th to 6th, 29 ; 5th to 6th, 21""" ; 6th to 7th. 



7th to 8th, I l : Mil to 9th, 1 l : 9th to ldth. 10' : LOtfa to I 1th. 



11th to [2th, 8™; 12th to LSth, 7 ; L3th to end. 7 : in all. 



