Famih'es of Telcostean Fishea. 177 



Suborder X. A C A N T II r T E \\ Y G 1 1. 



Air-bladder usually without open duct. Opercle well deve- 

 loped ; supraoccipital in contact with the frontals. Pectoral 

 arch suspended from tlio skull ; no niesocoracoid. Ventral 

 iins thoracic or jugular, the pelvic bones more or less firmly 

 attached to the clavicular arch. Gill-opening usually large ; 

 if small, in front of or above the base of the pectoral fin. 



The character from which this suborder, the most com- 

 prehensive of the whole class, derives its name, viz. the 

 jiresence of non-articulated, more or less pungent rays lu 

 the dorsal and anal fins, is by no means universal, exceptions 

 to the rule beino; numerous. The mouth is usually bordered 

 by the premaxillaries to the exclusion of the maxillaries, and 

 if these should, by exception, enter the oral edge, they arc 

 always toothless. The ventral fins are sometimes inserted 

 at some distance behind the base of the pectorals (Ilaplo- 

 dactylida^, Platycephalidffi), in which case, however, this is 

 merely due to the elongation of the pelvic bones, which are 

 solidly attached to the clavicular arch. The suborder is 

 broken up into 9 divisions, which follow in somewhat ar- 

 bitrary order, the natural affiuities being opposed to a linear 

 arrangement. 



I. No suborbital stay, or process extending from the suborbital bones 



towards the prasoperculum ; basis crauii double in the symmetrical 

 forms. Primary shoulder-girdle composed of a perforate scapula 

 and a coracoid ; of the four or five pterygials, or basal bones of 

 the pectoral fins, only one or two are in co.itact with the 

 coracoid ; ventral hns thoracic. 

 Enys of the caudal fin not strongly forked at 

 the base ; hypural usually with a basal 

 spine or knob-like process on each side ; 

 epipleural bones usually inserted on the 

 parapophyses or on tlie ribs ; dorsal fin 

 usually with strong spines ; caudal peduncle 



rarely much constricted I. Pkrciformes. 



Rays of the caudal fin strongly forked at the 

 base, embracing a considerable portion of 

 the hypural, which always bears a basal 

 spine ; epipleural bones usually inserted on 

 the centra or on the parapophyses, rarely 

 on the ribs ; dorsal spines feeble or de- 

 tached ; caudal peduncle much constricted ; 



scales usually very small or absent If. Scombriformes. 



Rays of the caudal fin not strongly forked at the 

 base, no hypural spine, and ventral finswitli 

 one spyie and six to eight soft rays, or 

 cranium asymmetrical III. Zkouuombi. 



II. No suborbital stay ; basis cranii double ; scapula abseut, the 



pterygials inserted on the coracoid ; ventral fins thoracic. 



IV. KURTIFORMES. 



Ann. cf' Mag. N. Hist. Ser. 7. Vol. xiii. 12 



