312 Annals of the Smith African Museum. 



Atlantic, while the fine Ophiothrix aristulata, which seems to unite 

 the Cape deep waters with those of the southern coasts of Australia, 

 is also known from the East Indies and Indian Ocean. As for the 

 South American connections, the Ophiomyxa of Agulhas Bank may 

 not be the South American species, so that Gorgonoeephalus chilensis 

 is the only species actually common to the two regions. 



The 57 species included in the present report belong to 11 families. 

 They can be most easily distinguished from one another if these 

 families are first differentiated, which the following key attempts to 

 do. Thanks to the brilliant work of Matsumoto, the families of 

 brittle-stars are now beginning to take on tangible form. Under 

 each family will be found a key to its South African representatives. 



Key to the South African Families of Ophiuroidea. 



Disk and arms covered with a smooth skin ; upper arm plates rudimentary or 

 wanting; side arm plates ventral or subventral in position. 



Arms simple, not very long, 3 5 times disk-diameter, not capable of vertical 

 coiling ...... Ophiomyxidae, p. 313. 



Arms branching, or if simple, very long, capable of being vertically coiled. 

 Teeth present in a vertical series on each jaw tip; arms not annulated 

 with bands of microscopic hook-bearing granules Trichasteridae, p. 314. 

 No true teeth; arms annulated with double series of hook-bearing granules 



Gorgonocephalidae, p. 315. 



Disk and arms not covered by a smooth skin ; upper arm-plates usually well- 

 developed ; side arm-plates not ventral or subventral in position (except when 

 upper arm-plates are unusually wide). 



Arm-spines moderately or quite long, more or less at right angles to long 

 axis of arm, never minute or closely appressed. 



Upper arm-plates small, more or less triangular, in contact (if at all) 

 only at base of arm; teeth triangular or sharply pointed; oral papillae 

 well-developed, 3 or more on each side . Ophiacanthidae, p. 319. 



Upper arm plates well-developed, forming a more or less continuous 

 series, or if triangular and discontinuous, then teeth broad, squarish and 

 oral papillae only 1, 2 or on each side. 



Dental papillae none; two proximal oral papillae may occupy tip of jaw. 

 Not more than 4, often only 2 or 3, oral papillae on each side 

 of jaw ..... Amphiuridae, p. 325. 



5 oral papillae on each side of jaw Ophiochitonidae, p. 343. 

 Dental papillae present in a cluster at tip of jaw. 



No oral papillae . . . Ophiotrichidae, p. 335. 



Oral papillae several 'on each side of each jaw 



Ophiocomidae, p. 347. 



Arm-spines small or at least slender, often minute, closely appressed to side 

 arm-plates. 



Disk closely granulated (rarely some plates are visible); arm-spines 5 10, 

 short, subequal. .... Ophiodermatidae, p. 349. 



