54 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 124 



trends are encountered not only in the more elongate zoarceoids, but 

 also in the congrogadoids. 



In regard to what would seem to be primary phylogenetic differ- 

 ences (fig. 12), the Blennioidei appear to be divisible into three main 

 groups: a notothenioid, a zoarceoid, and a trachinoid-blennioid- 

 congrogadoid series. These three groups (see fig. 12) are contrasted in 

 table 2. 



In many respects, evolution within the three groups has progressed 

 along parallel fines; for example, in the progressive fusion of elements 

 of the caudal skeleton. On the other hand, the same trend of develop- 

 ment may occur in all three, but apparently has progressed at different 

 rates. Thus, among the notothenioids, the medial extrascapular 

 remains free of the parietal in all of the forms I have examined except 

 Harpagifer; in the trachinoid-blennioid-congrogadoid series, it fre- 

 quently fuses with the parietal; and in the zoarceoids there is no 

 trace of a free medial extrascapular. Finally, there are indications of 

 secondary convergence of characters in the three series, as among the 

 pelagic and the burrowing forms already noted. 



But for all these difficulties, the three do show certain primary 

 differences in evolutionary development. Thus, the notothenioids have 

 tended to flatten the head and anterior portion of the body. Probably 

 associated with this are peculiarities of paired fin structure. With the 

 exception of certain sand-diving trichonotids, the pelvics are well 

 separated and maintain a full complement of five soft rays, with the 

 inner usually the longest; these pelvics normally are held back flat 

 against the body. In the pectoral girdle, the actinosts are always 

 broad and platelike, and the uppermost frequently fuses with the 

 scapula. In the above features, the notothenioids have developed along 

 lines that are not duplicated elsewhere in the Blennioidei. Conversely, 

 the notothenioids retain certain percoid features that most of the 

 other members have lost. Of these, the independent medial extra- 

 scapular already has been mentioned. More important, the para- 

 sphenoid in notothenioids (fig. 10a) has no wing extending in front of 

 the prootic in such a way as to exclude the prootic from the internal 

 orbital border. 



The notothenioids have, morphologically speaking, the longest 

 lineage in the Blennioidei. They extend from the Parapercidae, the 

 most percoid-like family of the Blennioidei, out to the Callionymidae 

 and Gobiesocidae. The latter groups show quite clearly all the trends 

 of notothenioid development listed above (except that the Gobiesocida 

 have only four pelvic rays), and the specializations that seem to 

 warrant their exclusion from the Perciformes altogether lie along other 

 lines. 



