450 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



slightly downward, and bears a series of strengthened scales armed 

 with a single keel, along which eight or fewer rather strong spinnles 

 project outward and backward. The occipital ridges are subparallel 

 anteriorly, but diverge posteriorly; the least distance between them 

 is contained 1.8 (1.5 to 1.9) times in the interorbital width; the scales 

 on the occipital ridges bear from one to three (usually one) spinous 

 carinae, but are rougher in small specimens. The median occipital 

 scute bears a single keel in the type and in the larger paratypes, but 

 three ridges in the small paratypes; a similar scute is situated at the 

 origin of the lateral line. A row of enlarged scales, the largest of 

 all, is located midway between the occipital and postorbital ridges; 

 these large scales have seven or fewer divergent carinae; the remain- 

 ing scales between those ridges are small or minute. The space be- 

 tween the front half of the occipital ridges is covered by five series 

 of scales; the scales of the median series are the largest, and bear 3 

 (2 to 4) divergent carinae; those of the outermost series on each side 

 are smaller, and bear 2 or 3 carinae; those of the intervening series 

 are minute. The two series of sparsely spinulate scales bounding the 

 median rostral series on each side become narrow anteriorly, so that 

 their lateral margins converge forward and meet the median series 

 just behind the terminal plate. A conspicuous scaleless groove sepa- 

 rates these series from the single series bounding the supranarial 

 ridge. An area of scales like those of the body is located behind the 

 upper half of the orbit. 



The first dorsal spine is sharp, but very short; the second spine is 

 produced into a filament, and is almost as long as the head in the 

 type. The base of the first dorsal is slightly longer than the length 

 of the interdorsal space in the type, and is contained from 0.9 to 1.2 

 times in that distance in the paratypes. The anterior rays of the sec- 

 ond dorsal fin are comparatively w T ell developed, being 0.3 as long as 

 the orbit. The origin of the anal fin is directly below that of the 

 second dorsal. 



The length of the fin rays forms a notable sexually dimorphic 

 character. They are decidedly longer in the males than in the 

 females, as is indicated in the following table: 



Table of measurements <>f length of fins in each sex. 1 



Second dorsal spine. 



Pectoral fin 



Outer ventral ray... 

 Second ventral ray . 



Males 

 (Paratypes). 



0.8 to 0.9 



1.15 to 1.50 



1.3 to 1.4 



Ca. 2.4 to 2.7 . . 



Females. 



Paratypes. Type 



1.17 to 1.55. 

 1.60 to 2.15. 

 1.7 to 3.0... 

 2.9 to 3.7... 



1.02 

 1.80 

 1.95 

 3.27 



1 Expressed in the number of times the length of each ray or fin is contained in the head. 



