92 FISHES. 



to tlie trunk, accompanying the lateral line. In many fishes 

 those of the infraorbital ring are much dilated, protecting the 

 entire space between the orbit and the rim of the prffioper- 

 culum ; in others, especially those which have the angle of 

 the prteoperculum armed with a powerful spine, the infra- 

 orbital ring emits a process towards the spine, which thus serves 

 as a stay or support of this weapon {Scorpmnidm, Cotticlce). 



The fcctoral arch of the Teleosteous fishes exhibits but a 

 remnant of a primordial cartilage, which is replaced by two 

 ossifications,-^ the coracoid (.51) and scapula (52) ; they offer 

 posteriorly attachment to two series of short rods, of which 

 the proximal are nearly always ossified, wliilst the distal 

 frequently remain small cartilaginous nodules hidden in the 

 base of the pectoral rays. The bones, by which this portion 

 is connected with the skull, are membrane-bones, viz. the 

 clavicle (49), with the postclavicle (49 -|- 50), the suprctclavicle 

 (47), and post-tcm2Joral (46). The order of their arrangement 

 in the Perch has been described above (p. 59). However, 

 many Teleosteous fish lack pectoral fins, and in them the 

 pectoral arch is frequently more or less reduced or rudi- 

 mentary, as in many species of Mura:nida\ In others the 

 membrane-bones are exceedingly strong, contributing to the 

 outer protective armour of the fish, and then the clavicles 

 are generally suturally connected in the median line. The 

 postclavicula and the supraclavicula may be absent. Only 

 exceptionally the shoulder-girdle is not suspended from the 

 skull, but from the anterior portion of the spinous column 

 (Symbranchidm, ]\Iurcenida\ Notacanthida:). The number of 

 basal elements of each of the two series never exceeds five, 

 but may be less ; and the distal series is absent in Siluroids. 



The puhic bones of the Teleosteous fishes undergo many 

 modifications of form in the various famiLies, but they are 

 essentially of the same simple type as in the Perch. 



1 Parker's nomenclature is adopted here. 



