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TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



Good figures of the skull of Cheilodactylus spectabilis are given by Leighton Kesteven 

 (1928, pp. 334-343). Its special interest Is that the short deep skull and very short, strong 

 jaws carry the serranid type a long way toward the nibbling specialization seen In the 

 chaetodonts, acanthurids and many still more- specialized derivatives of the predaceous 

 percoids. Its extremely short dentary forks over a short V from the articular In the manner 

 seen in labrids, scarids and other strong biters. The teeth are small and numerous and 

 could easily give rise either to the chaetodont or to the beaked condition. In view of this, 

 it Is not surprising to read in Boulenger (1910, p. 664) that these fish "feed chiefly on 

 crustaceans, molluscs, and other invertebrates living among sea-weeds." 



In Chironemus marmoratus, according to Frost (1928a, p. 451), the sagitta resembles 

 that of Perca generally but differs in certain details. 



Pseudoscarus guacamaia 



Fig. 134. Pseudoscarus. Rear view of skull, showing pharyngeal mill. 



Chiasmodonts. — These highly voracious deep-sea swallowers have had a checkered 

 taxonomic history, having been pushed about from one order to another; however, the 

 recent thorough study of the osteology by J. R. Norman (1929) seems to have put them 

 definitely In the suborder Percoidea as defined by Tate Regan, but in a new division, 

 Chlasmodontiformes Norman, coordinate with the Perclformes, etc., of Regan. The chief 

 osteological peculiarities are found in the mouth parts, there being an emargination in the 

 upper jaw between the expanded anterior portions of the premaxillae. Our Figure 137.^^ 

 is taken from a young skull of Chiasmodon kindly placed at my disposal by Dr. William 

 Beebe. Figures B, C, D, are from the paper by Mr. Norman. Analogues with some of 

 the large predatory scopelolds are evident In the slenderness of the premaxillae, etc. The 

 opercular elements are largely membranous. 



