i8- 



over the ends of the basal rays, or it may be regularly curved in its lateral thirds but nearly 



straight in its median third ; the middle of the dorsal surface of the lBr x is occupied by a large 



prominent broadly oval well rounded tubercle ; the axillaries are broadly rhombic with the 



lateral angles truncated so that the lateral edges 



are from one half to two thirds the length of 



the sides of the IBi^, two and one half times as 



broad as long, in the median line nearly twice 



as long as the IBrj ; the centre, except at the 



anterior angle, is occupied by a tubercle which 



is more elongated dorsoventrally than that on 



the IBr^ and, though as high. less prominent as 



it rises much less abruptly; the lateral edges 



of the IBrj and the IBr„ are turned slightly 



outward ; the lateral thirds of the proximal edge 



of the axillaries and the corresponding portions 



of the distal edge of the \Br l are also turned 



upward to the same height as the lateral edges ; 



the eversion of the latter is most marked just 



over the ends of the basal rays and gradually 



decreases anteriorly to the distal corner of the 



lateral edge of the axillary; it is continued thence 



along the sides of the first four brachials ; the 



inner lateral eclges of the first five brachials are 



similarly modified. 



The arms are, in the type, 165 mm. long. 



The first brachial is wedge-shaped, slightly 

 longer exteriorly than interiorly, twice as broad 

 as the exterior length; the proximal border is 

 narrowly produced ; the outer border is produced 

 like the lateral borders of the axillaries; the 

 inner border is similarly produced, especially at 

 the distal angle, which is more or less rounded 

 off and overlaps the proximal inner angles of 

 the second brachial. The second brachial is about 

 the size and shape of the first, with the outer 

 edge similarly produced ; the production of the 

 inner edge is like that of the outer, but not so 

 marked. The third and fourth brachials form a 

 syzygial pair which is oblong, about twice as 

 broad as long, with the lateral edges turned outward as in the brachials preceding; the following 

 brachials are slightly wedge-shaped, about twice as broad as long; one brachial between the 



Fig- 7- 

 Lateral view of a specimen of Perüsometra timoretisis from 

 Stat. 297. Natural size. (Courtesy of the U. S. National Museum). 



