140 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL.9 



In truth, there is no known genus of the Atherinopsinae with which 

 Alelanorhinus appears to have any close relationship, and we are disposed 

 to believe that it may not be phylogenetically close to this subfamily. We 

 therefore erect for this genus the new subfamily Melanorhininae. The 

 characters to which we especially wish to draw attention are the fol- 

 lowing: 



The body is exceedingly compressed and deep for an Atherinid, much 

 more so than in any genus of the Atherinopsinae, and the silvery lateral 

 band is absent. The head is short and "truncated," but showing no rela- 

 tionship to Eurystole, and the pelvic fins are placed nearer to the upper 

 angle of the pectoral base than to the anal origin. The mouth is smaller 

 than in any genus of Atherinopsinae, being greatly restricted at the ricti 

 by the lip membranes; but the premaxillaries are excessively protractile, 

 their posterior processes long and strong. The preorbital region and snout, 

 back as far as the eyes, are scaleless. The dentary bones, in spite of the 

 small mouth, are long, and their lower surfaces are rather strongly con- 

 cave. From all other genera of Atherinidae known to us, Melanorhinus 

 differs in the excessive development of scaly axillary or alar flaps. These 

 are composed of highly modified, greatly elongated, asymmetrical scales, 

 several of which make up each flap. The pectoral flap, originating just 

 above the upper angle of each pectoral base, is especially noticeable, and 

 extends for half the length of the fin. Each pelvic fin has a flap, of about 

 half its length, originating just above the outer, anterior edge of the fin 

 origin. Between the two pelvics is another, azygous flap, extending nearly 

 to the ends of the inner rays. Most remarkable of all are the flaps at each 

 side of the base of the spinous dorsal fin ; these are shorter than the others 

 and resemble the rather similar structure in Mugil. In fact, Melano- 

 rhinus somewhat closely resembles Alugil in appearance, although there 

 is certainly no direct relationship to the gray mullets. Both the soft dorsal 

 and the anal bear a sheath of a single row of somewhat elongate scales on 

 the bases of the rays, the sheath of each fin reaching the end of the fin 

 base. The scales of Melanorhinus are most peculiar. They are heavy, 

 closely adherent, and very hard to dislodge. In form, those of the mid- 

 sides are twice as deep as long, the apical border irregularly crenulated, 

 and the basal margin almost straight but with a small projection near 

 the middle. The circuli are reduced to vertical marks on the hidden sec- 

 tor of the scale, but the visible sector bears concentric striations very 

 much finer than the circuli. No well-defined nuclear area is present. Fi- 

 nally, Melanorhinus differs from most Atherinids in the greater number 



