ASTROSCHEMA TENUE. 27 



Astroschema tenue sp. nov. 



Special Marks. — Arms slender, and in length more than thirty times the 

 diameter of the disk. Radial ribs narrow and running to the centre. Disk 

 and arms smoothly granulated. 



Description of an Individual — Diameter of disk, 6™". Length of arm, 

 200'""'-. Width of arm near base, l.S""-. Teeth wider than long, with a 

 curved cutting edge. The general granulation becomes coarser on the 

 mouth-angles, and some of the larger grains extend upward on the sides of 

 the mouth-slits. Arms very slender and long; above and on the sides the 

 joints are indicated by gentle swellings, but the lower surface is flat. The 

 upper surface of the disk presents ten narrow radial ribs which meet in the 

 centre ; the disk margin between the ribs is re-enteringly curved. Upper 

 disk and arms closely granulated with smooth grains, whereof there are eight 

 or nine in a mm. long ; on the i-adial ribs they are somewhat coarser. The 

 lower side of the arm has a much finer and more scattered granulation. 

 Each of the first two pairs of tentacle-pores has a single small, thorn-like 

 tentacle-spine ; the pores beyond have two. Towards the middle of the arm 

 the tentacle-spine nearest the median line becomes much longer and larger, 

 1""' long, and has a club-shape, with fine thorns at its end ; while its fellow 

 retains its previous form. The mouth-tentacles project from little tubes, 

 which may also be seen on the pores of the base of the arm. Genital open- 

 ings standing close together at the inner angle of the interbrachial space and 

 separated by a partition. 



Color, in alcohol, nearly white. 



Hassler Expedition ; Barbadoes, 100 fathoms. 



This species stands nearest to A. oligactes, from which it is readily distin- 

 guished by the longer and more slender arms, and by a granulation smooth 

 and fine, instead of coarse and pointed. 



In a former paper [Annales des Sc. Nat.. 1872, p. 5) I expressed a doubt of 

 the distinction made by Dr. Liitken between Astroschema and Astromorpha, 

 founded on the position in the last genus of the genital openings in a hoUoiv. 

 By examining numerous alcoholic specimens of A. oligactes, I have been con- 

 vinced that this is not a valid difference. The real peculiarity in these, as 

 well as in Ophiocreas, is that the genital openings are at the inner angle of 

 the interbrachial space and are nearly vertical, instead of being horizontal 

 and placed alongside the arms. The genus Astromorpha may therefore be 

 merged in Astroschema. 



