30 ASTROPHYTON SPINOSUM. 



9th, 15"™-; 9th to 10th, 16°™ ; 10th to 11th, 16""'- ; 11th to 12th, 15"" ; 12th 

 to 13th, 15"™-; 13th to 14th, 13°"°-; 14th to 15th, 12'""-; 15th to 16th, 13"™-; 

 16th to 17th, 12-°» ; 17th to 18th, 10"""-; 18th to 19th, 8"™ ; 19th to 20th, 

 7-^-; 20th to 21st, 7°"°-; 21st to 22cl, e™"-; 22d to 23cl, 6"™ ; 23d to 24th, 

 gmm.. 24th to end, 5°™-. Teeth, mouth-papillEe, and tooth-papilte all similar 

 and spiniform ; they are sharp and slender, in number twenty or more, and 

 form a close high clump on the mouth-angle. Arms, near the disk, wide and 

 flat below and covered by a smooth skin ; above, arched and invested with a 

 fine smooth granulation about six grains in the length of a mm. On the 

 upper median line there is to each joint a row of four or five little spines 

 about .5""- long; and at their base there usually is a large rounded grain 

 {Fiff- 47). These spines are found well out on the arm. The terminal twigs 

 have their joints marked by annular ridges, each composed of a double row 

 of grains, which support little booklets. The depression between the joints 

 is covered by a double row of rounded grains {Fig. 46). Disk strongly in- 

 dented along its margin, and having deep radiating furrows on the back. 

 Its skin is smooth except a number of small spines like those on the back of 

 the arms, which are sparsely scattered in twos and threes over the upper 

 surface. At the inner angle of each of the interbrachial spaces is a madre- 

 poric shield. There is no trace of tentacle-spines near the base of the arm ; 

 but, outside the fifth fork, there are two or three to each pore, similar in 

 shape to those on the upper surface of the arm. Tentacle-pores closely con- 

 tracted, and only recognized by the little pits that mark their position. 

 Eadial ribs high and wide, occupying a large part of the upper surface ; 

 extending to the centre of the disk and projecting over the arms. 



Color, in alcohol, purplish-brown. 



Panama ; brought up by Wesley Clark, a noted diver, and presented by 

 Mr. Landsberg. 



This new species represents, on the Pacific side, A. costosmi of the West In- 

 dies, although it differs widely in its details. A. costosum has a few thick 

 stumps on the upper disk and the radial ribs, while A. spinosiim has clumps 

 of minute spines. 



Cambridge, January 1.3, 1875. 



