154 Cincinnati Society of Natural History. 



thickening of their upper extremit}' gives the species a somewhat 

 swollen appearance in this region. 



Brachials — Two or three, similar in shape to the radials, the lower 

 one nearl}^ equal to them in size, gradually tapering above. These are 

 followed hy five or six other plates of quadrangular shape, ver}- grad- 

 ually tapering upward, somewhat longer than wide. The seventh or 

 eighth is pentagonal, higher than wide, and upon its upper sloping 

 surfaces, the first bifurcation of the arms takes place. But three of 

 the rays can be clearl}^ traced to this point, and the}^ are bifurcated 

 upon the seventh and eighth plates above the radials. 



The equal shape and size of these plates, and the peculiar form of 

 the body, make it somewhat difficult to say where the brachial series 

 ends. 



Azygous Plates — These are not shown in either of the specimens 

 studied, but the area is indicated on the under side of the specimen 

 figured, though not so as to. make an understanding possible. 



Arms — First five, then ten, if all the rays divide as do the three 

 shown. After the second division, the subsequent ones can onl}^ be 

 traced in two rays, owing to the manner in which the arms are folded 

 together in the specimen. In one case the right hand portion continues 

 without further division to the eighth plate. The left hand again div- 

 ides upon the seventh arm plate, and aoain upon the ninth above 

 this. If there are any further divisions they are not shown. There 

 arise thus, from the divisions of this ray, six arms at the free ex- 

 tremity. If the other raj^s follow this plan, we shall have thirtj- arms 

 at the least. It is probable that the number is greater even than this. 

 The arms are slender, very gradualh' tapering, and much exceed in 

 length those of any other species of the genus of equal size. They are 

 entirely difl'erent from those o{ H. juvenis, Hall, the only species with 

 which this one need be compared. 



Pinnulce — There are no evidences of either pinnulse or the so called 

 " armlets" of other species of this genus. 



Column — Round, or very obscurely pentagonal, and much resembling 

 that of H. juvenis, Hall, as it is made up of an alternation of single, 

 solid discs, and five small, interradially placed pieces, for a distance of 

 one inch at least below the body. The size of the column is equal to 

 the greatest diameter of the latter. No greater length of the column 

 has been found. 



Ventral Sac — Not shown in the specimens studied. As I have 

 found it to be largely developed in H. constrictus, Hall, and H. simplex. 

 Hall, I have no doubt of its presence in this species. 



