830 



Mr. C. T. Eegan on the 



This classification was adopted by Jordan and Evermann 

 (Bull. U.S. Nat. Mus. xlvii. 1896, p. 707) except that the 

 subfamilies were given family rank. The diagnostic cha- 

 racters were practically unchanged, except that the position 

 and size of the additional bone in the lower jaw were correctly 

 indicated. Ridewood (P. Z. S. 1904, ii. p. 72) has pointed out 

 that the names "addentary^^ and " intradentary '^ proposed 

 by Gill were based on a misconception ; the best name for this 

 bone is that given by Ridevvood, namely " sesamoid articu- 

 lare.^' The development of this bone is more or less propor- 

 tional to the length of the jaw and the strength of the 

 dentition ; it is largest in Tylosunis and smallest in Exoccetus 

 {cf. text-fig.) . None of the characters used by Gill to charac- 

 terize his two families is really distinctive. In Scombresooe 



Inner view of left ramus of lower jaw of : 1. Eaoccetus arcttceps. 

 2. Chriodorus atherinoides. 3. Scomhresox saurus. 4. Belone belone. 



s, sesamoid articulare ; ar, articulare ; em, angulare ; d, dentarj. 



the form of the maxillary and its mode of attachment to 

 the prsemaxillary are exactly as in the Belonidae, and the 

 pharyngeal bones and teeth are much more similar to those 

 of Belone and Tylosurus than to those of Hemirhamphus or 

 Exoccetus [cf. PI. IX.). Zygapophyses are equally well 

 developed in all the Synentognaths ; throughout the group 

 the neural arch of each vertebra has on each side a posterior 



