ASTROPHYTOX SPINOSUM. 29 



20S mm -. It had more abundant granulation on the upper surface of the 

 disk, but was otherwise similar to the one first described. 



Hassler Expedition ; off East Patagonia, lat. 44° 52' S., long. 64° 10' W., 

 and lat. 51° 26' S, long. 68° 5' W., 55 fathoms. 



This fine Astrophjton belongs to the group whose arms are narrow at their 

 base, and the forkings few and distant. The species of cold and temperate 

 waters fall in this group, such as A. eucnemis, A. Lamarcldi (which resembles 

 the one under consideration), and A. Agassizii. The second group, whose 

 types are A. costosum and A. spinosum, has the arm wide at its base, and 

 divided often and at short intervals ; its habitat is in tropical seas. "Where 

 the one would have a width of 8 mm -, and a dozen or fifteen forks in the arm, 

 the other would have 14 mm - and twenty-five or thirty forks {Figs. 41 and 44), 

 whereof three would be within the disk, which is not circular, but deeply 

 re-entering at each interbrachial margin. 



What are spoken of as tentacle-spines are so named from their proximity 

 to the pores. They might be called also arm-spines, because they are car- 

 ried by the rudimentary side arm-plates, as may be seen in a young Astro- 

 phyton (Liitken, Additammta ad Hist. Ophiurid., PL I, PI. II. f. 17, b). The 

 booklets, or small spines, which stand on annular ridges and usually in 

 double rows, on the arms of all Astrophytid^e {PI. IV. f. 4-% 46, 51, -56), are 

 not immediate homologues of arm-spines, but are comparable to skin gran- 

 ules. Among Ophiuridfe, however, such booklets are true arm-spines {PI. 

 IV. f. eo, />■■ Ophiothela mdicola), attached to side arm-plates (*'). 



Astrophyton spinosum sp. nov. 

 PI. IV. f. 44-46. 



Special Marls. — Interbrachial spaces of disk deeply indented. Eadial 

 ribs thick and high. Little clumps of three or four spines at each joint on 

 the upper median arm-line. Arm forked three times within the disk. No 

 tentacle-spines on the pores near the base of the arm. Five madreporic 

 bodies lying at the inner angles of the interbrachial spaces. 



Description of an Individual. — Diameter of disk, 42™" . "Width of arm where 

 narrowest, inside disk, 15 mm \ Width of largest branch, outside disk, % mm \ 

 Total length of arm, measured along its branches, 28S mn \ to wit : from 1st to 

 2d (both within margin of disk), 14 mm ; 2d to 3d, 14 mm ; 3d to 4th, 14 mm - ; 4th 

 to 5th, 16 mm -; 5th to 6th, 15 mm -; 6th to 7th, 18 mm ; 7th to 8th, 15 mm -; 8th to 



