474 SYDNEY E. JOHNSON 



The hypural is a fan-shaped bone with a straight caudal edge 

 which has a deep median notch. ' Six fully developed, segmented, 

 and unbranched caudal rays and one rudimentary ray articulate 

 with the upper part of the hypural; the remaining five rays are 

 fully developed and articulate with the lower part. In the av- 

 erage adult specimen the rays are about 9 to 14 mm. long, the 

 inferior rays being the shortest and the middle ones the longest. 

 The uppennost ray bears a row of spines on its dorsal margin 



(fig. 14). 



The interneural spines decrease gradually in length from before 

 backward. They have prominent lateral ridges, are wedge- 

 shaped ventrally, and have large backward-pointing heads for 

 articulation with each other and with the dorsal spines and rays. 

 The first interneural spine is very large and probably represents 

 the ankylosed first two since it supports the first two dorsal 

 spines (fig. 14). 



The dorsal spines, eight in number, are weak and slender. 

 The last one is very short (about 1.3 mm.) and may easily be 

 overlooked. The longest are 5 to 7 mm. and the first bears 

 delicate spines on its anterior edge. The proximal ends of the 

 spines are expanded into large, rounded heads which articulate 

 in sockets or grooves of the intesneurals (fig. 14). 



The rays of the second dorsal are much more strongly devel- 

 oped, ranging from 7 to 10 mm. in length. The first has spines 

 on its anterior edge, and most of the others have delicate spines 

 on their sides (fig. 14). 



Except for being a little more slender, the interhaemal spines 

 do not differ from the interneurals. There are six, and the last 

 one bears the last two anal rays. The superior end of the first 

 lies between the lower ends of the first two haemal spines. The 

 last one is exceedingly short and slender. 



The anal rays are like the dorsal, segmented and unbranched. 

 They range in length from 6 to 12 mm., the longest being in the 

 middle. Seven is the usual number, although specimens were 

 observed which had but six . 



