310 A. E. Verrill — North American Ophiuroidea. 



g. — Oral shield transversely elliptical, rhombic, or quadrant- 

 shaped, broader than long. 



h. — Arm-spines 5 or 6, unequal, the lowest longest. Disk-scales 

 minute, not in a rosette. Tentacle scale large, ovate. Oral 

 shield elliptical. A supplementary oral scale is often 

 present. 



A. grandisqumna Lym,, '69. W. Indies. 



Jih. — Arm-spines 3, equal or subequal, tapei'ed. Disk-scales not 

 minute, forming a rosette. Tentacle scale small, flat. Oral 

 shield quadrant-shaped. A supplementary oral scale is 

 often present. Radial shields broad, in contact distally. 



A. limaris Lym., '78. W. Indies. 



gg. — Oral shields longer than bi'oad, oblong or ovate. Tentacle- 

 scale minute. Arm-spines 3 to 5, short, subequal. Radial 

 shields small, divergent. 

 i. — Disk-scales not minute, unequal, with edges rounded and ser- 

 rulate, forming a rosette, oral shield small, subovate. Under 

 arm-plates wide shield-shaped, little longer than broad. 



* A. Sundevalli M. and Tr. Gulf of St. Lawrence. 



ii. — Disk-scales minute, oral shields rather large, ovate. Under 

 arm-plates oblong, much longer than broad. 



A. SUm2)soni Ltk., '59, W. Indies. 



AA. — Tentacle-scales absent or rudimentary. 



j. — Disk destitute of scales below, or only partly covered. 

 Radial shields divergent, pear-seed-shaped or wedge-shaped. 

 = Ophiopelte Sars, Ljung. 



h. — Arm-spines six or seven, short, straight. Disk-scales minute, 

 not in a rosette. 



I. — Arm-spines seven, lowest short and stout, others flattened, 

 subequal. A supplementary outer oral scale. Oral shield 

 obtusely angulated or convex distally and proximally. 

 Dorsal arm-plates triangular, with the distal end verj' con- 

 vex ; five middle spines flattened and denticulated. 



*^. denticulata Koehl., '96. Off Newfoundland. 



