2G TELEOSTOML 



dd. Vertebra amphicoelian (double concave); maxillary not transversely 

 divided; scales cycloid BLalecomobphi, 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 fins (if present) abdomi- 

 nal, without spines, their basilar segments rudiuiental. (Soft-rayed 

 fishes.) (I'hysostomi.) 

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

 (supraseapula) ; form not eel-like. 

 fj. Prsecoracoid arch, present. 



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



subopercle nor symplectic bone ; four anterior vertebrae much 



modified, co-ossified, and with an ossicula auditus; supraoccipitals 



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



hh. Maxillary bone perfect, not entering into a barbrl (rarely entirely 



wanting); subopercle and symplectic bone present. 



»'. Anterior vertebra; modified, co-ossified, and with the ossicula 



auditus Evextogxathi, XII. 



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



ossicula auditus Isospoxdyli, XIII. 



gg. Pra?coraeoid arch obsolete: anterior vertebrte not modified; parie- 

 tal bones separated by sapraoccipital; head scaly. 



Haplomi, xrv. 



ff. Shoulder girdle not attached to the skull; no praecoracoid 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.) 

 (1'lnjsoclysti.) 



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



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

 line on side of abdomen Syxextogxathi, XVI. 



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

 spines.) 



I. Gills tufted; pharyngeal bones and most of the branchihyals want- 

 ing; skin with bony plates Lophobraxchii, XVII. 



//. Gills pectinate (as usual in fishes). 



m. Superior branchihyals and pharyngeals reduced in number ; 



ventrals sub-abdominal Hemibranchii, XVIII. 



mm. Superior branchihyals and phanmgeals in normal development. 



n. Ventral fins abdominal Pekcesoces, XIX. 



nn. Ventral fins thoracic or jugular. 

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

 p. Bones of the jaws distinct. 



q. Cranium normal Acaxthopteri, XX. 



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

 of head; no fin spines. . . Hetep.osojiata, XXI. 



