'214 ANATOMY OF VERTEBRATES. 



ib. c, arising from tlie outer j^iart of the scapula and from the 

 parapophyses of succeeding vertebras, is inserted by similarly 

 disposed, but more slender tendons. At their termination, each 

 tendon bifurcates, allowing that appropriated to the succeeding 

 vertebra to pass through it, so that all, save the last, are both 

 perforati and ■perforuntes. The protractor scapula, ib. i, be- 

 comes, when antagonised by the two foregoing muscles, the 

 chief elevator of the head. Of the two muscles of the ros- 

 trum in the Ray, the siiperior, levator rostri, arises from the 

 scapula by a short fleshy Ijelly ending in a slender round tendon 

 which runs above the branchia; in a synovial sheath to the rostral 

 cartilage, which it serves to raise : the inferior, dcprcHsor rostri, 

 arises from the lower part of the coalesced anterior vert el)ra3, runs 

 obliquely outward, and then curves inward to its insertion into the 

 lower ])art of the liase of the rostrum. The muscles of the jaws 

 in the Kays include, with 'inaxillo-mandilulares, those answering 

 to I and lit in the Shark, fig. 132. The depressor mandibuU is a 

 large oblong mass of parallel hmgitudinal filires, arising from the 

 lower (coracoid) part of the scapular cincture, and passing forward 

 to be inserted into the raid part of the mandilile. Two small mus- 

 cles, one on each side, contribute to depress the mandilile : they 

 are attaclied in front near the commissure of the lips, and, running- 

 inward, almost cross each other beneath the great depressor. A 

 third muscle has its fibres remarkably interlaced, but divisible into 

 three chief fascicles, two of which arc anterior and one posterior : 

 this is derived from the end of the upjter jaw and joins the hinder 

 margin of the second mass. The first portion is situated in front 

 and abo\e the maxilla, near its conmiissurc, and riuis obliquelv to 

 join the outer edge of the second fixscicle : all co-operate in firndy 

 closing the mouth. Tlie p>rotractor oris forms a pair of long and 

 slender muscles passing from the rostrum l:)etween the cranial base 

 and tlic palate to be inserted into the maxilla. The muscles of 

 tlie vast pectoral fins form two thick fleshy layers, covcrinn- its car- 

 tilages above, fig. 139, t, and below, and dividing into as many 

 fasciculi as there arc fin-rays, into which they arc inserted. A 

 similar arrangement obtains in the muscles of the ventral fins, ib. i\ 



The muscles, in Fishes, of the eye-ball, the air-bladder, and of 

 some other special organs, will be described with tlie parts they 

 move. 



The nuiscular tissue (rayonine) of fishes is usually colourless, 

 often opaline, or yellowish ; white when boiled : the muscles t>f 

 Ihe j)ectoral fins of the Sturgeon and Sliark are, however, dee]ier 

 coloured than the others ; and most of the nuisclcs of the Tunny 



