ORDER TELEOSTEI. 



993 



or placed in advance of the pectorals. The fin-rays may or may 

 not be articulated ; and there are never fulcra on the fins. There 

 are two pairs of nasal openings on the top of the head. Other 

 characters are found in the soft parts which are not usually avail- 

 able in the case of fossils. 



It may further be observed that Teleosteans agree with Ganoids 

 in the hyostylic structure of the skull, and that cranial bones and a 

 secondary pectoral girdle (fig. 844) are always developed. The 

 arrangement of the cranial bones in a typical Teleostean is shown 

 in fig. 930, where it will be seen that the preopercular (Pr) does not 



Fig. 031. — Skeleton of the Perch {Percajiuviatilis). Reduced. Letters as in fig. 836, p. 91 



extend on to the face as it does in some Ganoids. In certain forms, 

 however (Siluridce), the cranium develops large bony plates, articu- 

 lating with others in the cervico-dorsal region, and presenting a 

 striking resemblance to some of the cartilaginous Ganoids. In the 

 same group strong spines, articulating with the underlying bones, are 

 developed in the pectoral and dorsal fins ; while the Salmonoids, many 

 Siluroids, and others develop behind the rayed dorsal an additional 

 fin without rays, to which the name adipose ox fatty fin is applied. 



According to Dr Gunther's classification, the Teleostei are divided 

 into six suborders, but other writers would group the last five of 

 these together under the name of Physoclysti, as of equivalent value 

 to the first, or Physostomi. The former arrangement will be fol- 

 lowed here, but only such families as are of importance to the 

 palaeontologist can be noticed. 



Suborder i. Physostomi. — In this suborder the swim-bladder, 

 when present, is connected by a duct with the pharynx ; the pelvic 

 fins are generally abdominal in position, and have no spine ; while 

 all the fin-rays are articulated, but sometimes only the first rays of 

 the dorsal and pectoral fins are ossified. This suborder comprises 



