344 A. E. Verrill — North American OpJiiuroidea. 



varies in form, however, even on the different jaws of the same 

 specimen. It is usually ovoid, or obtusely lanceolate, or even 

 obovate ; sometimes it is acute or mucronate at tip, and then it 

 differs a little more decidedly from the teeth. It stands on the tip 

 of the dental plate. 



The oral and adoral shields are thickened and prominent, shaped 

 nearly as in the figure by Mr. Lyman. The oral shield is small and 

 somewhat fan-shaped, or rather pelecoidal, for the inner lateral 

 edges are strongly incurved. In one specimen the oral shields were 

 unusually narrow and acutely angled proximally. The adoral 

 shields are relatively large, lunate, confined to the proximal side of 

 the oral shield. 



First under arm-plate is small, irregularly six-sided, strongly 

 emarginate within. The second is much broader than long, curved 

 distally, and obtusely angled proximally. Those following are still 

 shorter, transversely narrow-elliptical, with a very obtuse proximal 

 angle, or nearly truncate and broadly curved distally, often showing 

 a slight median incurvature of the edge, which becomes more dis- 

 tinct on those farther out. They are thick and widely separated by 

 the side arm-plates, which lie in grooves. More distally they become 

 more nearly square, with the inner end more angulated. 



Tentacle-scale small, spiniform, subacute, rather rough, becoming 

 more slender farther out. All the tentacle-pores are small. 



Arm-spines about as figured, except that many of them are more 

 thorny, especially those near the base of the arms and in the upper 

 series, most of which have irregular sharp divergent thorns ; farther 

 out they are mostly minutely serrulate. They are not usually dis- 

 tinctly flattened, as stated, but slender, terete, tapered, acute. The 

 rows are closely approximate dorsally on the second and third joints, 

 becoming separated farther out. 



Upper arm-plates thick, swollen, widely separated, rather triangu- 

 lar or quadrant-shaped, with an obtuse proximal angle and a broadly 

 convex distal edge. On the middle of the proximal part there is a 

 small, wart-like elevation. 



Diameter of disk of those described above, 3 to G""". 



Off St. Vincent, 88 and 124 fathoms. Blake Exped. 



Ophiacanthella Verrill, 1899a, p. 39. Type, 0. Troscheli (Lym.) Ver. 



Three terminal tooth-papilla? in a group. Radial shields long, 

 narrow, largely in contact, more or less naked. Disk-scales obscured 

 by cuticle, granulose or spinulose. No special oi'al tentacle-scales. 



