A. M Yerrill — JVort/i American Ophmroidea. 321 



O. Troscheli (Lym.) Arm-spines six, tapered. Disk-scales con- 

 cealed, bearing granules and scattered spines. Tentacle-scale single, 

 lanceolate. 



00. — Ophioscalus Ver., 1899a, pp. 39; 42. Dorsal arm-plates sepa- 

 rated. Basal rows of spines closely approximate dorsally. 

 Radial shields large, broad, naked, in contact for their 

 whole length. Two or three tooth-papillae. Arm-spines 

 thorny and glassy. 



0. echinulata Lym. Disk-scales small, nearly concealed by numer- 

 ous slender, thorny spines. 



AA. — The oral shield is separated from the side arm-plates by the 

 distal lobe of the elongated adoral shields, which are there- 

 fore, not entirely proximal to the oral shields. 



D. — Adoral shields narrow, trilobed, the narrow distal lobe separat- 

 ing the oral shield from the side arm-plate. Disk-scales 

 ixsually concealed by cuticle and spinules. 



E. — Ophiopora Ver., 1899a, p. 43. No tentacle-scales, the pores are 

 very large; spines small, usually smooth. 



0. Bartletti (Lym.) Ver. One spiniform distal oral papilla by the 

 side of the oral tentacle-j)ore. Disk covered with acute spinules. 



EE. — One or two tentacle-scales. 



p. — OphioUmna Verrill, 1899a. Arm-spines seven or eight, 

 nearly smooth, placed obliquely on the distal part of the 

 plates, not strongly divaricate. Jaws more or less granu- 

 lated. Disk-scales and radial shields concealed, bearing 

 granules and spines. 



* 0. Bairdii (Lym.) Ver. LTpper arm-plates separated. Rows of 

 spines approximate dorsally. Tentacle-scale single. 



0. mixta (Lym.) Ver. Upper arm-plates joined. Rows of spines 

 wide apart dorsally. Two flat tentacle-scales. 



j)2). — Ophiopristis Ver., 1899a. Arm-spines serrulate, not obliquely 

 placed. Strongly divaricate. Dorsal arm-plates separated. 

 Tooth-papilloB usually three. 

 q. — Spines partly flattened, serrulate on the edges. A row or 

 cluster of several distal oral papillae at the large oral tenta- 

 cle-pore. Two tentacle-scales on the basal joints. 



