THE OPHIURIDiE. 



185 



West Indies, the most important difference being tliat the plates of the 

 dorsal side are here perfectly smooth, whereas they are tuberculated in 

 >S'. mmrhina. Also the coloring is different. 



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f 



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62. Asteronyx dispar n. sp. 



r 



r 



Plate XXI. Figs. 1-3. Plate XXII. Figs 10 13. 



This species so closely resembles A. Loveni, M. & Tr, that no close de- 

 scription is needed ; we need only to note the differences. 



The essential feature is that the arms are unequally developed, usually 

 two being distinctly narrower and shorter than the other three. In a speci- 

 men of 17 mm. diameter of disk, the longest arm is about 300 mm. ; the two 

 shortest, about 150 and 200 mm. The large arms are considerably broader 

 on the middle part than at the base. In younger specimens the arms are 

 more alike. They are not so high as in A. Loveni, and have a more ringed 

 aspect, the skin being so delicate that the arm-bones are plainly seen 

 through it. The side arm-plates are rather prominent, more than m 



A. Loveni. , j • 



There are 6-7 hook-like arm-spines, the lowermost being prolonged m 



the middle part of the arm, clad with skin, and with spines at the end, as in 

 A Loveni These elongated spines are found only in large specimens, of 

 about 20 mm. diameter of disk, and only in the broad part of the large arms. 

 Several specimens from Stations 3354, 322 f . ; 3392, 1270 f . ; 3393, 

 1020 f • 3398, 1573 f. ; 3402, 421 f. ; 3407, 885 f. ; and 3431, 995 f. 



» 



63. Asteronyx excavata n. sp 



Plate XXII. rigs 8-0 



Diameter of disk, 18 mm. ; width of arms close to disk, 3 mm. ; arms of 

 different length; in the described specimen the shortest is about 110 mm., 

 the longest al least 200 mm. The longest arms are also larger than the 

 shorter,°and they are broadest in the middle part, as in A. dispar. 



Mouth region as in A. Loveni, the mouth papilla) only being somewhat 

 more obscured by the skin. The arms have a rather curious aspect : the 

 side arm-plates are narrow, elongated, directed downwards, enclosed m and 

 connected by a naked skin ; they make thus a fence along each side of the 

 arm, whose under side therefore appears deeply excavated. In side aspect 





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