PISCES. 



959 



prinidse, remain for a long time only attached 

 by suture to the bodies of the vertebrae, from 

 which they are easily distinguished. 



In certain Fishes, as, for example, in Merlus, 

 the transverse processes are very large and give 

 attachment to the swimming bladder. Some- 

 times the ribs are suspended from the trans- 

 verse processes, or sometimes they are derived 

 immediately from the bodies of the vertebrae. 

 In this respect there are great varieties. 



In those vertebrae that are situated behind 

 the abdominal cavity there is an inferior fora- 

 men for the lodgement of the great blood- 

 vessels of the trunk bounded by inferior spinal 

 laminae (hamapophyses), and, like the superior, 

 generally supporting long spinous processes, 

 (fig. 493, 5,) so that the vertebra? seem to consist 

 of similar parts, both above and below the body. 

 These inferior arches of the caudal vertebrae 

 are considered by Cuvier as being formed by 

 the inordinate developement of the transverse 

 processes, which he describes as here becom- 

 ing directed downwards and united to each 

 other, so as to form the inferior ring ; and, 

 certainly, in the generality of Fishes, by tra- 

 cing the apparently gradual conversion of the 

 abdominal into the caudal vertebrae, such is 

 the conclusion at which the comparative anato- 

 mist would naturally arrive. In many Fishes, 

 however, as, for example, in the Muraenidae, 

 these inferior arches with their appropriate 

 spines are in the caudal region co-existent with 

 distinctly developed transverse processes, evi- 

 dently shewing that they must be regarded as 

 being totally different elements of the skeleton, 

 namely, the haemapophyses. (See OSSEOUS 

 SVSTEM.) 



The inferior or haemapophysial elements, like 

 the superior arches, have in many instances 

 oblique processes developed from them, which 

 in some cases are very large and branched, so 

 as to form a kind of interlacement around the 

 vascular canal. This is especially observable 

 in certain Tunnies. 



As the vertebrae approach the tail, their pro- 

 cesses are gradually shortened, and the verte- 

 bral canal becomes narrowed or obliterated, 

 (Jig. 493, 8,) and at length the terminal vertebrae 

 have their apophyses consolidated with each 

 other and with the interspinous bones, so as to 

 form in some Fishes, as the Perch, a vertical 

 triangular plate, to the posterior margin of which 

 are articulated the rays of the caudal fin (9). 

 In Fishes with long and pointed tails like the 

 Eels this disposition is wanting; but in other 

 races, such as the Pike, the real composition of 

 this part of the skeleton is easily recognisable. 

 Ribs and sternum. The ribs of Fishes have 

 nothing to do with respiration, merely serving 

 to support the muscular parietes of the body ; 

 they consist of the dorsal portion only, which 

 is articulated by a single head, either to the 

 transverse processes or to the bodies of the 

 vertebrae themselves. Frequently they give off 

 long bony processes, which penetrate among 

 the muscles; and sometimes also similar pro- 

 cesses are attached above the ribs to the bodies 

 of the vertebrae themselves, so that the flesh of 

 some Fishes appears full of little bones as fine 



as hairs. The ribs vary extremely in different 

 genera. Sometimes they are round and slen- 

 der, sometimes compressed and falciform ; 

 occasionally they seem to surround the whole 

 abdomen, and in many species are quite rudi- 

 mentary or altogether wanting. The sternum 

 is entirely deficient in most Fishes ; sometimes, 

 however, it does exist, as in C/upea, Vomer, 

 &c. ; in such cases it consists of a longitudinal 

 series of impair bones, differently shaped in 

 different genera, to the sides of which the ribs 

 are attached inferiorly. 



Cranium. The cranium of osseous Fishes, 

 when all its parts are completely developed, is 

 made up of no fewer than twenty-six bones, six 

 of which are azygos, viz. the basilar, the principal 

 sphenoid, the anterior sphenoid, the vomer, the 

 ethmoid, and the interparietal or superior occi- 

 pital ; and twenty are in pairs, namely, the 

 J'rontal, the anterior frontal, the posteriorj'ron- 

 tal, the parietal, the mastoid, the external occi- 

 pital, the lateral occipital, the petrous, the great 

 alar and the lesser alar bones ; but as these 

 have all been described and figured in a pre- 

 ceding article, and their homologies with the 

 cranial bones of the other vertebrate classes 

 fully discussed, (vide OSSEOUS SYSTEM, Comp. 

 Anat., vol. iii. p. 826,) it would be superfluous 

 to dwell upon them more at length in this place. 

 Bones of the face. The bones of the facial 

 apparatus have likewise been pointed out and 

 figured in the article above referred to. They 

 consist, when the series is complete, of the fol- 

 lowing pieces, which, seeing the extremely vari- 

 ous forms of the face in this class of animals, 

 present innumerable varieties as regards their 

 developement and relative importance, notwith- 

 standing that their general arrangement is tole- 

 rably persistent throughout the class. 



The maxillary (fig. 436, 18, vol. iii. p. 826) 

 and the intermaxillary (fig. 436, 17) form the 

 anterior boundaries of the face and circumscribe 

 the anterior and lateral limits of the mouth : the 

 latter, however, is in Fishes the most important 

 bone of the two, and is most commonly armed 

 with teeth, while the former is very generally 

 destitute of dental organs, and being imbedded 

 in the fleshy substance of the upper lip, has been 

 called by some authors the labial bone or os 

 mystacis. It is indeed upon the relative shape 

 and size of the intermaxillary bone that the 

 form of the upper jaw of Fishes principally de- 

 pends, and in some cases, as for example in 

 the Sword-fish (Xiphias), Lepidosteus, &c. these 

 bones are enormously prolonged anteriorly, so 

 as to form an elongated beak or powerful ros- 

 trum which constitutes a formidable offensive 

 weapon. 



The face of Fishes, properly so called, is 

 made up of several bony pieces very variable 

 both in their size and number, which have been 

 named the pranasal (fig- 436, 20,) the subor- 

 bitul(fig. 436, g, g, g,) and the supra-temporal 

 bones ; all of these, however, with the exception 

 perhaps of the praenasal, belong to the exoske- 

 leton (vide vol. iii. p. 845.) In the hard-cheeked 

 Fishes ("joues cuirassees" of Cuvier) these 

 osseous plates are enormously developed, and 

 indeed form a kind of bony mask enclosing all 



