112 Bulletin, Vanderbilt Marine Museum, Vol. IV 



with rounded cutting edges. The under arm-plates are as long as 

 broad, with the outer margin wider than the inner, the corners 

 rounded; the lateral margins are reenteringly curved where the ten- 

 tacle scale fits. The side arm-plates are strongly developed and bear 

 stout projections carrying the arm-spines. The arm-spines are in 

 series of five ; the uppermost one is the longest ; all are long, slender, 

 sharp, somewhat flattened, with about nine or ten spines on each 

 margin. The dorsal arm-plates are small, about as long as broad, with 

 the inner margin relatively straight and shorter than the outer margin 

 which is decidedly convex, the lateral margins are straight and 

 sloping. 



References: Ophiothrix suensonii Lutken, Yid. Med., p. 16, 1856; 

 Add. ad Hist. Oph., pt. II, pi. 4, fig. 12 a-e, p. 250, 1861.— Lyman, 

 Mem. Mus. Comp. Zool., I, p. 157, 1864. — H. L. Clark, ibid, 

 XXV, p. 279, 1915; Bull. Mus. Comp. Zool., LXII, p. 313, 

 1918-19. 



Family: OPHIOCOMIDAE. 



Genus : OPHIOCOMA L. Agassiz. 

 Ophiocoma aethiops Lutken. 



Plate 65. 



Type: Lutken 's type was obtained at Panama and is deposited in 

 the Copenhagen Museum. 



Distribution : The tropical west coast of America from Lower Cali- 

 fornia to Panama and also at the Galapagos Islands. Littoral. 



Material examined : Five very large specimens, collected in "Webb 

 Cove, Albemarle Island, Galapagos Islands, in a tide-pool, February, 

 1928, by the "Ara." 



Color: Black, occasionally mottled with grayish. 



Technical description : Brittle star, large, arms stout. Disk diam- 

 eter 34 mm. ; arm length 125 mm. Abactinal surface and surface of 

 interbrachial regions covered with fine round granules, which are 

 much finer than those of its "West Indian congener, Ophiocoma 

 echinata. Mouth-shield small, squarish with angles rounded, forming 

 a broad oval nearly circular. Side mouth-shields fitting close around 

 the mouth-shields, meeting in the middle. Mouth papillae eight or 

 nine; one very wide blunt tooth nearest the jaw angle, followed by 

 two longer, narrow, blunt papillae and then a cluster of three shorter 

 papillae at the apex. Teeth strong with truncated tips. 



