32 



BULLETIN 75, UNITED STATES NATIONAL MUSEUM. 



radial shields, and three or four interradial in each interradius, one 

 of which is a very large marginal plate. Radial shields widely sep- 

 arated, oval, slightly wider at outer end. First two or three upper 

 arm plates quadrilateral, much wider than long; succeeding plates 

 in contact with each other, but with proximal side becoming shorter 

 and shorter until each plate is triangular and separated from its fel- 

 lows. Interbrachial spaces below covered with about fifteen plates, 

 of which a marginal one is decidedly the largest. Oral shields with 

 a proximal angle, but rounded distally, about as long as wide. Adoral 

 plates wider at outer end, meeting within; oral plates small and 

 indefinite. Oral papillae, four or five on each side, the penultimate 



FIG. 6. OPHIO'ZONA ELEVATA. X6. o, FROM ABOVE; b, FROM BELO<V; c , SIDE VIEW OF THREE ARM 



JOINTS NEAR DISK. 



much the largest. Teeth about five; lowest much the smallest. 

 First under arm plate very much wider than long, about one-fourth as 

 large as second, which is somewhat pentagonal, with a rounded distal 

 angle, about as long as wide or longer ; third to eighth plates about 

 as wide as long or wider, imperfectly pentagonal, gradually becoming 

 triangular, more or less in contact with each other; succeeding plates 

 triangular, rather longer than wide, separated from each other. Side 

 arm plates large, slightly swollen, meeting above and below beyond 

 eighth to tenth joints; each plate carries two arm spines, the upper 

 decidedly the longer and nearly as long as a joint. Tentacle scales, 

 two, or occasionally three, quite small. Color (dried from alcohol), 

 dull purplish-brown, irregularly and indistinctly marked with darker 



