— 51 — 



Turning backward in the myodome it lies at first dorso-lateral to the rectus internus, but it extends 

 posteriorly beyond that muscle, into the basioccipital part of the myodome. Near the hind end of 

 this latter part of the myodome, the muscle becomes tendinous and is inserted on the basioccipital, 

 certain of the fibers of the tendon passing out of the myodome, by its posterior opening, and there 

 arising from the ventral, external surface of the bone. The orbital opening of the myodome is closed 

 by a strong membrane which the recti muscles all perforate to reach their points of origin. 



Sagemehl says that, in the Characinidae, the recti inferior and externus arise in the myodome, 

 the internus having its origin in the orbit; and as the myodome, in the Cyprinidae, is said to difEer 

 in no important respect from that in the Characinidae, these muscles must there have the same 

 origin. In all of the mail-cheeked fishes that I have examined, and also in Scomber (Allis, '03), it 

 is the externus and internus instead of the externus and inferior that have this origin in the myodome. 



CAROTID ARTERIES AND VESSEL X. 



The external and internal carotid arteries were traced both in 45 mm specimens and in the 

 adult, and they differ but little from the arteries in the adult Ophiodon elongatus, recently described 

 by Allen ('05). I, however, find, in young specimens of Scorpaena, Trigla, Lepidotrigla and Dacty- 

 lopterus, a small artery that is not described by Allen, that would seem to be in part the homologue 

 of the hyo-opercularis artery of my descriptions of Amia ('97, p- 497), and that has already been 

 referred to as the vessel x. 



The external carotid of Scorpaena, after its origin from the short common carotid, runs upward 

 and forward, enters the trigemino-facialis Chamber through its facialis opening, and traversing that 

 Chamber issues by its trigeminus opening. It then immediately gives off what must be the sclerotic- 

 iris artery of Allen's descriptions, though the artery as I find it has not exactly the distribution given 

 by Allen. It then gives off a brauch to the levator arcus palatini muscle and the large facialis-maxil- 

 laris artery, as described by Allen in Ophiodon, and itself turns downward and slightly backward 

 in the V-shaped space between two flanges on the hind edge of the metapterygoid, to be later des- 

 cribed. At the lower edge of the internal one of these two flanges the artery falls into the arteria 

 hyoidea at a sharp bend in that artery, that part of the carotid that lies between the point where 

 it gives off the facialis-maxillaris and the point where it falls into the arteria hyoidea, corresponding 

 closely in position to the secondary afferent pseudobranchial artery of my descriptions of Amia 

 ('00 c). The hind end of the latter artery, in larvae of Amia, closely approaches the dorsal end of the 

 primary affferent pseudobranchial artery, which artery is the arteria hyoidea, and if the secondary 

 afferent artery should acquire a connection with the arteria hyoidea, and that artery retain its con- 

 nection with the pseudobranch, the conditions found in Scorpaena would arise. And this is quite 

 certainly the manner in which the teleostean arrangement has actually arisen. 



The arteria hyoidea of Scorpaena, Coming upward along the ceratohyal, turns dorso-anteriorly 

 along the anterior aspect of the interhyal and traverses a large opening that lies between the pre- 

 opercular and the posterior process of the quadrate, posteriorly, and the symplectic anteriorly. 

 There it immediately gives off the mandibular artery, which runs downward and forward, along 

 the outer surface of the quadrate, into the mandible. Having given off this artery, the arteria hyoidea 

 turns sharply upward, crosses the external surface of the hyomandibulo-symplectic interspace of 

 cartilage and at the antero-dorsal corner of that cartilage passes in ward through a small opening 

 between the cartilage, the metapterygoid and the shank of the hyomandibular. Continuing its upward 



