A MONOGRAPH OF THE EXISTING CRINOIDS 215 



Geographical range. From the Bahamas and Dry Tortugas southward, through- 

 out the Caribbean Sea, to Bahia, Brazil. 



Bathymetrical range. From the shore line down to 355 meters. 



Thermal range. From 13.05 C. to 24.83 C. 



Remarks. The genus Nemaster represents a more generalized type than Capil- 

 laster, the relation between the two being approximately the same as that between 

 Neocomatella and Comatella. 



Nemaster is the only genus in the Comasteridae in which most of the species are 

 distinctively colored, the distinctive coloration consisting of lines or spots of dark 

 brown or black. Elsewhere in the Oligophreata such a condition occurs only in the 

 genus Mariametra (Mariametridae), and in the Macrophreata it is found only in the 

 genera Thysanometra and Coccometra (Antedonidae). 



The general structure of CapiUaster and Nemaster is quite the same, but the 

 interrelationships of the species included in these two genera are widely different. 

 The two largest species of Nemaster (grandis and iowensis), except for the much longer 

 brachials, resemble in a general way CapiUaster multiradiata, though both have 

 stouter cirri, which in one are long and in the other short. But the two small species 

 are delicate and slender with black markings a middorsal line in one (rubiginosa) 

 and saddle spots on the pinnule segments in the other (discoidea ) and do not in any 

 way resemble the species of CapiUaster. In Nemaster the cirri vary greatly in the 

 several species, but not at all in the same way that they vary in the species of Capil- 

 laster. They range from slender and delicate to very stout, and consist of from 10 to 

 35 segments; but in only one species (grandis) are there more than 20 cirrus segments. 



The arms are always less slender than in the species of CapiUaster, and they 

 may be (discoidea) exceedingly slender and attenuated. In length they vary, in adult 

 individuals, from 80 to 200 mm. The number of arms varies from 11, or possibly 10, 

 to 34, and seems to be exceedingly variable in each species. 



The species of this genus are subject to the same extreme irregularity in the 

 division series which is such a remarkable feature of the species of CapiUaster. 



KET TO THE SPECIES IN THE OENU9 NEMASTER 



a 1 . No conspicuous dark spot in the middle of each pinnule segment, the pinnules being unicolor or 

 with the tips of a different color from their bases; robust, or at least not markedly slender; 

 cirri XX-XXX, usually over XX; arms 18-43 in number, rarely less than 20. 

 6'. Stouter; no black median dorsal line on the arms; size usually large, the arms 90-200 mm. in 



length. 

 c 1 . Cirri with 30-35 segments; size large, the arms about 200 mm. long (east coast of Central 



America; 0-62 meters) grandis, p. 216. 



c 1 . Cirri with not more than 18 segments; small, the arms 90-130 mm. long (Bahamas and 



Florida to Dominica and Barbados; 1161 meters) iowensis, p. 218. 



6 2 . More slender; a conspicuous black line, sometimes interrupted, in the middle of the dorsal 

 surface of each arm; size usually smaller, the arms 80-105 mm. in length (Bahamas and 



Florida to Bahia, Brazil; 0-161 meters) rubiginosa, p. 225. 



a a . A dark spot in the middle of each pinnule segment so that the pinnules are conspicuously banded 

 with dark red or gray and white or yellow; no median black line on the dorsal surface of the 

 arms; very slender; cirri rarely over XX; arms not more than 20 (Caribbean Sea; shallow 

 water to 355 meters) discoidea, p. 232. 



