ACERINA SUHR.ETZEJ^ 



37 



and rather free. The openings of the cephalic canal, and the opercular 

 spines resemble those of Aceruia cermin. At the upper edge of the pre- 

 operculum are seven strong sharp spines, one at the angle, two on the under 

 edge, and four or five covered by skin. The operculum terminates in a 

 very pointed spine ; the sub-operculum only shows fine denticulations. 



The dorsal fin commences over the pectoral fin ; its bony rays rapidly 

 increase in height to the fourth, and then decrease gradually to the last, 

 which is about half the length of the succeeding soft rays, which are much 

 closer together than are the spinous rays. The anal fin is placed beneath 

 the soft portion of the dorsal fin, though its base does not reach back so 

 far. The anal aperture is in about the middle of the length of the body. 



^/////,.,, 



^7^ < . ...Mt^ 



ul^'" 



Fig. 13. — ACEUINA SCHK.KTZEK (LINN.TiL s). 



The pectoral fin is of irregular form ; the longest rays are the earliest. In 

 the ventral fin the strong spinous ray is only half the length of the suc- 

 ceeding soft rays. The hinder margin of the caudal fin is only moderately 

 concave ; the fin measures one-seventh of the total length of the fish. 



Scales are generally absent from the head and the regions of the 

 paired fins, though a few small scales are sometimes found in front of the 

 ventral fin on the breast. 



Thus it is seen that the chief distinctions in the tins of this species, other 

 than those of form, are in the dorsal containing nineteen sj^inous rays instead 

 of twelve or fourteen, while there is occasionally an additional ray in the 

 anal and the pectoral fin. 



The lateral line is parallel to the back, is on the upper fourth of the 

 side, and contains sixty to seventy scales. There are seven or eight rows 

 of scales above it, at the commencement of the dorsal fin, and thirteen or 

 fourteen rows of scales below it. 



