328 PROCEEDINGS OF THE CANADIAN INSTITUTE. 



Innervation. — The first is supplied by a branch from Tr. 

 branchicdis iii. vagi, and the second and third by a branch from 

 Tr. branchialis iv. of the same nerve. 



Action. — They will tend to approximate the arches, and also to 

 tilt the posterior ones upwards. 



In the Gyprinoids there are two sets of muscles, termed by Vet- 

 ter, ' obliqui dor sales inferior es] and ' obi. dors, superior es' In 

 Amiurus no such division can be made, nor is it possible to indicate 

 homologies between the forms. 



8. Musculi Transversi Dorsales, (Cuv. 34 and 39.) 



Exposed by removal of the preceding muscles and by the detach- 

 ment of the branchial arches from the skull. They are, like the cor- 

 responding ventral muscles, two in number. The anterior passes be- 

 tween the pharyngobrs. i., ii. and iii., of either side, the posterior be- 

 tween the ossa pharyngea superiora of opposite sides, the posterior 

 fibres passing into the fascia forming the posterior boundary of the 

 branchial cavity. 



Action. — Approximate the arches of opposite sides. 

 These muscles probably correspond with the transversi dorsales of 

 Perca, the anterior of which extends between epibr. ii., the posterior 

 between pharyngobrs. iii. and iv. of opposite sides. In the Cypri- 

 noids only a single muscle is present, which corresponds to the pos- 

 terior muscle in Amiurus. 



VI.— MUSCLES OF THE TRUNK. 

 These muscles, which are very numerous, one corresponding to each 

 intervertebral region, have usually been described as forming one 

 great muscle on each side, the great lateral muscle. This is conveni- 

 ent for description, the various muscles making up the great lateral 

 mass, being serially homologous and almost identical in appearance. 

 Each consists, in its typical form, of a muscular plate, (myomere), 

 the fibres of which run parallel to the long axis of the body, and arise 

 from and are inserted into a fibrous band (myocomma) 1 taking 



1 These terms are here employed in the same manner as by Wiedersheim in his lately pub- 

 lished " Handbueh der Vergl. Anat. der Wirbelthiere." As originally used by Owen, myoeom- 

 ura signified the muscle, the derivation being given as (co/u^a — a segment. As here used its 

 derivation will be from kowxol — a pause in a sentence. 



