Families of Teleostean Fishes. 167 



The structure of tlie skull conforms to that of typical 

 Malacopterygians. The prgemaxillary and maxillary are 

 both well developecl_, the latter placed behind the former^ and 

 forming but a very small part of the oral border ; the 

 symplectic is present ; the parietals form a long sagittal 

 suture and separate the frontals from the supraoccipital. The 

 vertebrte are very numerous, tlie pra^caudals bearing very 

 strong parapophyses, to which short slender ribs are attached. 

 The skin is naked (Symbranchidsp) or covered with minute 

 scales (Amphipnoida?), and the vertical tins are rudimentary, 

 reduced to mere dermal folds. 



Like the Apodes, these fishes are no doubt derived from 

 some low type with abdominal ventral fins, but whether from 

 the Malacopterygii or the Haplomi we have as yet no data 

 from which to conclude. 



Only two families : — 



Post-temporal well developed, forked, attaclied to 



the skull 1. Symbranchidcs. 



Post-temporal absent, the shoulder-girdle free from 



the skull , 2. Amphip)ioidce. 



Suboder IV. A P D E s. 



Air-bladder, if present, communicating with the digestive 

 tract by a duct. Pra^maxillaries absent ; the maxillaries, if 

 present, separated on the median line by the coalesced ethmoid 

 and vomer. Pectoral arch, if present, not connected with and 

 remote from the skull ; mesocoracoid arch absent. Fins 

 without spines, the ventrals absent. Anterior vertebrae 

 distinct, without Weberian ossicles. 



The Apodes, or Eels, are elongate serpentiform fishes with 

 naked skin or with minute scales imbedded in the skin, the 

 opercular bones small and completely hidden under the 

 integument, narrow or minute gill-openings, the vertical fins, 

 if present, confluent behind or separated by the projecting 

 tip of the tail. The pterygo-palatine arch is often reduced or 

 absent, and there is no distinct symplectic ; the supraoccipital 

 bone is small, separated from the frontals by the parietals, 

 which meet on the middle line. The vertebras are very 

 numerous (up to 225) and the prsecaudals bear strong para- 

 pophyses, to which short slender ribs may be attached ; 

 epnieurals are sometimes present. 



The five families into which this suborder is divided show 

 remarkable degrees of simplification in the structure of the 



