26 TELEOSTOML , 



(Id. Vertebrae amphicoelian (double concave); maxillary not transversely 



divided ; scales cycloid Halecomoepbi, X. 



aa. Arterial bulb thin, with a pair of opposite valves; optic nerves crossing, 

 not forming a solid chiasma. (Series Teleostei.) 

 e. Air-bladder (if present) connected by an air-duct with the intestinal 

 canal, this persistent throughout life ; ventral (ins (if present) abdomi- 

 nal, without spines, their basilar segments rudiinental, (Soft-rayed 

 fishes.) (Physostomi.) 

 f. Shoulder girdle attached to the skull by means of a post-temporal bone 

 (suprascapula) ; form not eel-like. 

 g. Prsecoracoid arch, present. 

 A. Maxillary bone imperfect, forming the base of a long barbel ; no 

 subopercle nor symplectic bone ; four anterior vertebra? much 

 modified, oo-ossitted, and with an ossicula auditus; supraoccipitals 

 and parietals co-ossified; no scales. . . Xematognathi, XI. 

 AA. Maxillary bone perfect, not entering into a barbel (rarely entirely 

 wanting); subopercle and symplectic bone present. 

 i. Anterior vertebras modified, co-ossified, and with the ossicula 



auditus EVEN'TOGNATHI, XII. 



ii. Anterior vertebriB similar to the others, separate, and without 



ossicuhi auditus Isospoxdyli, XIII. 



gg. Praecoracoid arch obsolete; anterior vertebrae not modified; parie- 

 tal bones separated by supraoccipital ; head scaly. 



Haplomi, XIV. 



ff. Shoulder girdle not attached to the skull; no prsecoracoid arch; 



parietal bones in contact; maxillary wanting or united with the 



palatines; form eel-like Apodes, XV. 



ee. Air-bladder without duct (in the adult) ; ventral fins without basal seg- 

 ments, usually anterior in position; spines usually present in the fins; 

 pectoral fins not on the plane of the abdomen ; parietal bones usu- 

 ally separated by the supraoccipital. (Spiny-rayed fishes chiefly.) 

 (Fhysodysti.) 

 j. Shoulder girdle connected to the skull by a post-temporal. 

 4. Lower pharyngeals co-ossified ; no spines ; ventrals abdominal ; lateral 



line on side of abdomen Stnentognathi, XVI. 



kh. Lower pharyngeals separate (or united, and the dorsal fin with 

 spines.) 



I. Gills tufted ; pharj'ngeal bones and most of the branchihyals want- 

 ing; skin with bony plates LOPHOEEAKCHII, XTII. 



U. Gills pectinate (as usual in fishes), 

 m. Superior branchihyals and pharyngeals reduced in number ; 



ventrals sub-abdominal Hemieranchii, XVIII. 



mm, Superior branchihyals and pharyngeals in normal development. 



n. Ventral fins abdominal Pekcesoces, XIX. 



im. Ventral fins thoracic or jugular. 

 0. Pectoral fins not pediculate, the gill openings in front of them. 

 p. Bones of the jaws distinct. 



q. Cranium normal Acanthopteki, XX. 



qq. Cranium twisted, so that both eyes are on the same side 

 of head; no fin spines. . . Hetekosomata, XXI. 



