GYMNODONTES. l?(i!) 



Fam. 2. GYMNODONTES. 



Gymnodontes, Cuv. Jicr/ne Animal. 



Body more or less shortened. The bones of th(^ 

 upper and lower jaw are confluent, forming a beak 

 with a trenchant edge, without teeth, with or without 

 median suture. A soft dorsal, caudal, and anal are 

 developed, approximate. No spinous dorsal. Pectoral 

 fins; no ventrals. 



Marine fishes of the temperate and trojjical regions. Some species 

 confined to fresh water. 



Si/noj)sis of the Groiqis and Genera. 

 First Group. Triodontina. 



Tail rather hn(/, with a separate camJ((I Jin ; abdomen diJatahle into 

 a large compressed sac, sujjported ,hij a lonj pelvic bone. Air- 

 bladder present. 



The upper jaw di-sided by a median suture, the lower simple. 



1. Triodon, p. 270. 



Second Group, Tetrodontina. 



Tail and caudal Jin distinct. Part of *he oesophagus much crtev- 

 sible, and cfipyahle of being Jilled ivith air. JS^o pelvic bone. 

 Air-bladder present. 



A. Bothjatvs divided hi/ a median suture. 



Dorsal and anal fins many-rayed 2. Ximoptcrus, p. 270. 



Dorsal and anal fins very short 3. Tetrodon, p. 271. 



B. Jaws vjithoiit Virdtan suture. 



Nasal tentacle simple, -^ith a pair of lateral opening-s. Dermal ossifica- 

 tions with a stiff but movpable spine .... 4. Diodon, p. oOG. 



Nasal tejitacle simple, with a pair of lateral openings. Most of the der- 

 mal ossifications three-rooted, with a stiff immoveable spine. 



5. Chilomyctcrus, p. 309. 



Nasal tentacle with two cylindrical and tapering branches ; no nostril. 

 Posterior dermal ossifications three-ruoted, with a stiff' immoveable 

 spine : 6. DicotijUchtliys, p. 314. 



Nasal tentacle as in IHcotylwhthys. All dermal ossifications with stilt" 

 moveable spines 7. Atopomycterus, p. 315, 



A nasal tentacle. Dermal ossifications very small, two-rooted, with a 

 fine flexible spine 8. TnchodiL'lc^i . p. 310. 



No nasal tentacle. Body covered with long hair-like bristles. 



9. Trichocyclus, p. 316. 



Tb^'-rl Group, Molina. 

 Body compressed, very short, not extensible by air : fail e.vtremrln 



