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FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



In the smallest larva, 2.2 mm. (fig. 8), this crest 

 bore three heavy serrations and extended over 

 only the anterior half of the supraocular region. 

 At 2.7 mm., this crest extended both posteriorly 

 and anteriorly over the entire top of the eye and 

 beyond. The serrations had increased in number 

 but decreased in strength. By 3.9 mm., the 

 crest extended farther around the eye to shield its 

 anterodorsal and posterodorsal arcs. By 6.6 mm. 

 (fig. 10), the serrations and the ridge itself were 

 becoming decreasingly prominent, and additional 

 serrate ridges were forming lateral to the medial 

 cranial crest. By 8.2 mm., the supraocular crest 

 had become more finely serrate and the additional 

 ridges were more prominent. By 12.1mm., (fig. 11) 

 all of these crests and ridges were disappearing 

 (probably being overgrown as they ceased to grow), 

 and by about 35 mm. only vague outlines could be 

 seen. These, too, were lost by 40 mm. 



Preopercular Spines 



Larval P. alius possess a strong, conspicuous, 

 ridged, and serrate spine at the angle of the pre- 

 opercle, flanked by two spines that are shorter and 

 less prominent (but also ridged). In the 2.2-mm. 

 larva (fig. 8), the angle spine reached nearly to the 

 anal opening. It became progressively shorter in 

 relation to the head length as the size of the fish 

 increased (actually it appeared to be overgrown as 

 the preopercle enlarged), until in individuals of 

 about 75 mm., it remained only as a heavy, pointed 

 projection, little more conspicuous by its length 

 than its immediate neighbors above and below. 

 Although its outlines were still discernible in the 

 largest adult examined (261.8 mm.), it lost its 

 significance as a spine in fish above about 75 mm. 

 Beginning with the largest larvae, and as the fish 

 enlarged, other spines also developed as strong 

 serrations on both limbs of the preopercle, in- 

 cluding the two shorter spines which originally 

 flanked the angle spine. The serrations increased 

 in numbers and strength with length of fish to 

 about 200 mm., after which they decreased. The 

 preopercle of the largest adults is only finely 

 serrate and the larger angle spines are overgrown 

 and visible only as outlines. 



Nostrils 



Formation of the paired nostrils was complete 

 (including a tube surrounding the opening of the 

 more anterior one of a pair on each side) in an 



8.2-mm. specimen. No external openings were 



discernible in a 6.6-mm. individual. 



Teeth 



Adults of P. alius possess irregular rows of small 

 canine or sharp-pointed peglike teeth on the 

 premaxillaries and dentaries. Similar small peg- 

 like teeth also occur on the tongue, vomer, and 

 palatines. The size at which these teeth form 

 was not determined, but all teeth were present 

 and obvious in a 19.9-mm specimen. 



At about 35 mm., a single row of rather widely 

 spaced canines, several times the size of their 

 neighbors, began to develop on the outer edge of 

 the premaxillaries and dentaries. As they first 

 appeared at about the size metamorphosis begins, 

 before the bottom habitat is assumed, and per- 

 sisted through the largest specimens examined, 

 their appearance may be related to a new diet. 



Fin-Ray Serrations 



The spines of the dorsal, anal, and pelvic fins 

 of the smallest pre juveniles develop ridges which 

 become rough due to small irregular projections. 

 These projections develop on the leading edge 

 of the single pelvic spine, and on alternate lateral 

 aspects of the dorsal and anal spines. The dorsal 

 and anal spines are heteracanthus (staggered) 

 in their insertions, and a spine that is heavy and 

 rough on its left side is more delicate and smooth 

 on its right. The next spine following is rough on 

 its right side and smootli on its left. In the larger 

 adults, the roughness tends to disappear, though 

 the alternating rough and smooth appearance 

 persists. 



The dorsal, anal, and pelvic soft-rays in the 

 smallest prejuveniles also develop the rough sur- 

 face on both sides, and this character persists in 

 lessening degree in the larger specimens examined, 

 though it is never completely lost. 



Branchiostegals 



A full complement of six branchiostegal rays on 

 each side was evident on a 2.7-mm. specimen, the 

 smallest stained. 



Vertebrae 



Ossification was first noted in the anteriormost 

 vertebrae in the smallest specimen (2.7 mm.) 

 stained. All vertebrae in a 4.8-nmi. individual 

 showed some degree of ossification, which prog- 

 ressed posteriorly. 



