ACANTHOPTERI. 397 



T. ACANTHOPTKRI. 



(The Spiny-rayed Fishes.} 



Cranium normal, symmetrical ; the maxillary bone distinct from the 

 premaxillary, which forms the border of the mouth. Bones of the 

 mandible distinct. Gills normal, laminated, rarely reticulated. Gill- 

 openings in advance of the pectorals. Opercular apparatus complete. 

 Basal bones of pectorals not enlarged. Pharyngeals well developed, 

 the third superior pharyngeal usually largest. Lower pharyngeals 

 separate or united. Ventral firs variously placed, often wanting, nor- 

 mally thoracic and six-rayed, the first ray spiuous. Anterior rays of 

 dorsal and anal normally developed as spines, but often soft and artic- 

 ulate. Air-bladder, if present, without pneumatic duct. The most ex- 

 tensive of the orders of fishes, comprising a great variety of forms. 



spine; -re/>v, fiu.) 



(Acanthopterygii, PkaryngognatM, and Anacantlrini Giiuthcr, i, ii, iii, iv, exclusive of 

 various families. Orders Pcrcesocis, Fcrcomorphi, and Pharyngognatki Cope, Trails. 

 Amer. Phil. Soc. 1870, 456.) 



ANALYSIS OF FAMILIES OF ACANTHOPTERI. 



A. Ventral lins abdominal; dorsals two, well separated. (Percesoces.) 



B. Dentition strong; vertebra; 24 ............................... SPHYR^ENID^E, 67. 



BB. Dentition feeble; vertebrae more than 24 ; carnivorous ....... ATIIERIXID^E, 68. 



BBB. Dentition feeble ; vertebra? 24 ; limnophagous ................ MUGILID.E, 65. 



AA. Ventral tins, if present, thoracic or jugular. 

 C. Ventral region without sucking-disk. 

 D. Suborbital without bony stay. 



E. Ventral fins present, the rays in normal number,* I, 5. 



F. Lower pharyugeal bones separate (except in certain Stianridas); gills 4, 



a slit behind the last. 

 G. Gill-membranes free from the isthmus. 



H. Spinous dorsal transformed into a lamellated sucking-disk, situated 



on the top of the head. 



ECHENEIDID^E, 70. 



HH. Spiuous dorsal not transformed into a sucking-disk. 

 I. Scales small or obsolete, mostly cycloid; spiuous dorsal compar- 



atively little developed; caudal 

 peduncle slender, t the fin widely 

 forked. t (Scombriform fishes.) 

 K. Vertebrae more than 24 or 25; no free anal spiius. 



L. Spiuous dorsal represented by free spines; caudal not forked; 



body elongate, fusiform. 



ELACATID^E, 71. 



* Except in certain Stromatciclcv, Acanthurlda', and Icosteidoa. 

 t Except in Pomatomidce, Elacatida;, aud some Stromatcidcc. 



