162 OPHIOTHRIX ANGULATA. 



Ophiothrix angulata Ayres. (P1. il. Figs. i-3.) 



Ophiurn angulata Say. Journ. Phil. Acad., V. p. 145. 1825. 

 Ophiothrix angulata Ayres. Proceed. Boston Soc. Nat. Hist., IV. p. 249. 

 Ophiothrix liispida Ayres. Proceed. Boston Soc. Xat. Hist., IV. \). 249. 



SiJecial Marks. — Pale bluish, with a white line along amis, and 

 bands across them. Disk about 6.5°"°'. Arm-spines numerous ; often 

 ten or eleven near base of arm. About eighteen tooth-papilla}. 



Description of a Sj^ecimen. — Diameter of disk, 6.4""" ; outer side of 

 mouth-shield to outer corner of opposite mouth-.slit, 2.8""°' ; width of arm 

 without spines, l.o""' ; length of arm, 38.4°"" ; distance from outer side 

 of mouth-shield to inner point of tooth-papilla?, to that between outer 

 corners of mouth-.slits as 1,6 : 1.4. Tooth-papilla? like a bunch of short, 

 stout, blunt spines, soldered by their sides ; arranged in five horizontal 

 rows, of which the three highest have each four spines, the lowest one 

 or two, and the other three ; papilla) often irregularly placed, not in 

 rows ; the papilla? on the sides of the rows project more towards centre 

 than do the middle ones. Teeth four, highest smallest, all thickened so 

 as to touch, or nearly touch, each other. Mouth-shields closely soldered 

 with side mouth-shields and with surrounding parts ; in shape nearly 

 oval, with a slight peak towards mouth ; length to breadth, .6:1; 

 madreporic shield larger. Side mouth-shields closely soldered with sur- 

 rounding parts, in shape elongated triangular. Under arm-plates some- 

 what square ; outer side a little re-enteringly curved ; laterals rather 

 strongly curved ; inner side nearly straight ; plates pretty closely sol- 

 dered with each other and with surrounding parts ; innermost plate 

 small, nearly heart-shaped, with its joint inward ; second plate contracted 

 at its inner end ; general form of other plates square, till near tip of 

 arm, where they gradually get more elongated, their lateral sides 

 straighter, and their outer sides more strongly re-entering ; length to 

 breadth (seventh plate), .5 :.6 ; about two thirds the length of the arm, 

 .4 : .2 ; close to tip of arm, same proportion, but plates smaller, the 

 breadths as above given ; show also the lengths of the outer sides ; the 

 breadth of the inner side of the seventh plate is .4""° . Side arm-plates 

 covered with skin, so that their outlines are obscured, ridge bearing 

 arm-spmes, high, narrow, and of even width. Upper arm-plates pretty 

 clearly marked, at base of arm ; each has four sides, an outer, much 

 curved, an inner, very short, and two lateral, nearly straight ; inner side 

 very short, so that plates seem like wedges, with their points turned 

 inward ; first two or three plates shorter than those that follow ; plates 

 near point of arm much elongated ; length to breadth as follows : first 

 plate, .6 : .6 ; sixth jDlate, .6 : .8 ; about two thirds the length of the arm. 



