THE CHARACTERISTICS OF THE DACTYLOPTEROIDEA. 



BY 



Thf.odore Gill, M. D., Ph. 1). 

 (With Plate xix.) 



The Dactylopterids, or mail cheeked fislies kuown as the flying gur- 

 nards, or, more vaguely, flyiug-fishes, so celebrated among navigators, 

 and of which we have so many accounts in their writings, have been gen- 

 erally placed in the family Triglida^ or with related forms by others 

 associated with those fishes. They differ, however, much more than do 

 the Triglidw and Peristedidw among themselves. In the words of Cu- 

 vier and Valenciennes, " it is even with diflBculty that we are able to find 

 any other character common to all of them than the extent of the 

 casque which protects their head, but even this casque has an entirely dif- 

 ferent form, it is long and wide, but at the same time flat and little ele- 

 vated. The snout is short and destitute of prominences. The enlarged 

 suborbital does not cover the entire cheek and articulates in a movable 

 manner with the preoperculum, so that the latter can spread out more 

 than in the Triglidcc, and thus the fish can avail itself in its defense of 

 the enormous spine which arms the inferior angle of the bone. The 

 operculum, on the contrary, is not spinous. The teeth of the Dactylop- 

 terids are small and paved, and they exist only on the jaws and not on 

 the vomer or palatines. Their branchial apertures are but little open, 

 and there are only six rays in their membrane.* They have only four 



* The exact words of Cuvier aud Valenciennes (v. 4, pp. 114, etc.) are as follows: 

 " Ces poissons, si c6Iebre8 i)arnii les uavigateurs, et dont taut de relations font 

 I'histoire, ont 6t6 g(5neralemeut plac6s dans le genre des trigles ; mais ils en different 

 beaucoup plus que les trois sous-genres dont nous venous de parler ne different entre 

 eux: c'est meme a peine si I'ou pourrait leur trouver d'autro caractere eommun que 

 lYiteudue du casque qui garautit leur tete ; encore ce casque a-t-il une tout autre 

 forme : il est long ot large, mais plat et peu 61ev6. Le museau est court et sans pro- 

 eminences. Le sous-orbitairo ue couvre pas toute la joue et s'articule d'une mani^re 

 mobile avce le pr«5opercule ; en sorte que celui-ci peut s'6carter phis que dans les tri- 

 gles, et que lepoisson peut profiter jiour sa ddfense d'une <5norme <5piue qui arme Pangle 

 infgrieur de cet os. L'opercule, au contraire, n'est pas dpineux. Les dents des dac- 

 tylopteres sont en petits pav6s, et ils n'eu ont qu'aus niachoires seulement, et non au 

 vomer ni aux palatins. Leur ouTes s'ouvrent peu, et il n'y a que six rayons dans leur 

 membrane. II n'y en a que quatre mous dans les ventrales; circonstauce trt-s-rare 

 parmi les acauthoptdrygiens. Los pectorales n'out point de rayons libres; mais elles 

 Proceedings United States National Museum, Vol. XIII— No. 818. 



243 



