THE SKULL OF OSSEOUS FISHES. 117 



consists simply of tlie cerato-branchial element ; but in Anobas 

 supports a pliaryngo-bx'anchial («6. 49). It is often expanded, and 

 usually more or less beset with teeth : it has been termed the inferior 

 pharyngeal bone {os pharyngien mfcrieure, Cuvier), as if it were 

 homologically distinct from the gill-bearing arches ; and in the same 

 insulated sense the upper expanded dentigerous portions of these 

 arches are termed by Cuvier the " os pharyngiens superieures :" they 

 are sometimes blended together into one piece, as in the Cottus. 



The peculiar cribriform or labyrinthic cavities, lined by vascular 

 membrane, and subservient to the continuance of respiration in 

 certain fishes, which can live long out of water, the Climbing Perch 

 {Anabas) for example, and other genera of the Order called by 

 Cuvier " Pharyngiens labyrinthiformes," are due to a peculiar deve- 

 lopment of the epi-branchial and pharyngo- 

 branchial pieces of the first, second, and some- 

 times the third branchial arches {fig. 39. 48). 



All these gill- and tooth-bearing arches ap- 

 pertain to the splanchno-skeleton, or to that 

 category of bones to which the hard jaw-like 

 pieces supporting the teeth of the stomach of 

 the Lobster belong. The branchial arches are 



Branchial arch, with laby- . -i • i i x i 



rinthic pharyngo-branchials SOmctimCS CartllaglUOUS whcU the trUC CUdO- 



skeleton is ossified : they are never ossified in 

 the perenni-branchiate Batrachians^ and are the first to disappear in 

 the larvae of the caduci-branchiate species ; and both their place and 

 mode of attachment to the skull demonstrate that they have no essential 

 homological relation to its vertebral structure. All the primitive six 

 pairs of branchial arches are present, but cartilaginous in the Lepi- 

 dosiren; and the last, which answer to the inferior pharyngeal bones 

 in normal Osseous Fishes, supports gills, and not teeth, whilst the 

 second and third arches have no gills in this remarkable fish : they 

 offer a striking contrast in tissue, connections, and development with 

 the strong, bony, persistent hyoidean arch of the true endo-skeleton. 



Scapular Arch {fig. 30. h, i, 50, 51, 52). 

 The fourtli cranial inverted arch is that which is attached to 

 the par-occipital ; or to the par-occipital and mastoid ; or, as in the 

 Cod, to the par-occipital and petrosal; or, as in the Shad, to the 

 par-occipital and basi-occipital : tluis either wholly or in part to the 

 par-apophysis of the occipital vertebra, of which it is essentially the 

 hfemal arch ; it is usually termed the ' scapular arch.' In the Eel 

 tribe, where it is very feebly developed, and sometimes devoid of any 

 diverging appendage, it is loosely suspended behind the skull ; and in 



I 3 



