A. JS. Verrill — North American Ophmroidea. 343 



Ophiomitrella Ver., 1899a, p. 89. (See p. 336, and p. 353.) 



Ophiomitrella laevipellis (Lym.) Ver. 



Ophiacantha Icevipellis Lym., Bull. Mns. Comp. Zool., vol. x, p. 259, pi. vi, 



figs. 82-84, 1883. 

 Ophiomitrella Icevipellis Verrill, Ophiur. Bahama Exped. , v, p. 39, 1899. 



About twenty specimens of this species were sent to me by Mr. 

 Lyman. They show considerable variation among themselves, and 

 all diifer more or less from his figures and description. 



The disk is strongly five-lobed, owing to a deep incurvature of 

 the interradial areas. The upper side is closely covered with small 

 thin scales, which are usually smooth and nearly destitute of gran- 

 ules, but in some examples there are a few scattered, low, verruci- 

 form grains, especially near the margins ; in others the grains are 

 thinh^ scattered over nearly all the surface ; in some cases part of 

 the grains are conical. The scales themselves vary somewhat in 

 size and distinctness. 



The radial shields appear to be long and narrow and nearly par- 

 allel ; a narrow ridge, in dry specimens, often runs inward nearly to 

 the center from each shield ; only the ends of the shields are com- 

 monly exposed ; this naked part varies in form and extent, but is 

 usually long, narrow, wedge-shaped, widest distally, and the ends 

 often project somewhat beyond the edge of the disk over the base of 

 the arm and may bear a few marginal granules. The ends of the 

 shields are sometimes near together, being separated by a space less 

 than half their breadth; in other specimens they are separated more 

 than their bi'eadth. 



Oral papillae vary in number, even on the different jaws of the 

 same specimen, from three to five ; most frequently there are three 

 in the regular series, with a smaller and much shorter distal one, just 

 at the distal end of the ad oral shield and above the large pore of the 

 outer oral tentacle. In many cases this outer papilla develops to full 

 size, like the next one, which is stout, erect, obtuse, larger than those 

 that follow it; the latter are usually compressed vertically, sub- 

 acute ; the inner one is a little longer and more conical. Attached 

 to each inner corner of the first arm-plate there is a small vertically 

 flattened scale or papilla that appears to be movable ; it guards the 

 oral tentacle on the inside and is sometimes wanting. It corresponds 

 to a similar process which in several other species seems immovable. 



Tooth-papilla one, or perhaps none, for the odd papilla at the tip 

 of the jaw agrees nearly in size and form with the true teeth. It 



