— 65 — 



that runs downward and backward to fall into the arteria hyoidea, as already described. The bind 

 edge of the external one of these two flanges abuts against, and is firmly bound to, the anterior edge 

 of the ventral half of the shank of the hyomandibular, the dorsal portion of the corresponding edge 

 of the internal flange being similarly connected with, but not abutting against, the anterior edge of 

 that thin portion of the hyomandibular, apparently of menibrane origin, that lies between the an- 

 terior articular process and the shank of the bone. The external flange is quite undoubtedly an 

 ossification of the metapterygoid menibrane of Amia, the thickened, process-like portion of the 

 flange being the homologue of the metapterygoid process of that fish (Allis, '97, p. 557). 



Across the anterior one third to two-thirds of the internal surface of the body of the 

 metapterygoid, at about the middle of its length, the entopterygoid extends, that bone lying at 

 an angle to the metapterygoid. The V-shaped Space between the two bones is filled by, and gives 

 Insertion to, a portion of the adductor arcus palatini. 



ECTOPTEKYGOID. 



The ectopterygoid is a slender bone, with two sharply pointed limbs lying at an obtuse angle 

 to each other. From the angle between the two limbs a thin and irregulär process projects dorso- 

 posteriorly, h'ing against the internal surface of the palato-quadrate cartilage, and, beyond that 

 cartilage, against the internal surface of the metapterygoid. The ventro-posterior limb of the; bone 

 is the shorter of the two, is bevelled and fits against the internal surface of the anterior edge of the 

 quadrate. The dorso-anterior limb fits upon the dorsal edge of the posterior portion of the ventral, 

 ectosteal flange of the palatine, and although but a thin and slender bone is grooved its füll length, 

 on its dorsal surface. This little groove lodges the ventral edge of a slender and rod-like portion of 

 the palato-quadrate cartilage, which connects the cartilages of the palatine and quadrate regions, 

 and, mesial to that rod of cartilage, lodges the ventro-lateral edge of the anterior portion of the 

 entopterygoid. 



ENTOPTERYGOID. 



The entopterygoid is a V-shaped bone, one limb of the V being small and the other large, 

 the point of the V directed ventro-laterally. The small lateral limb lies against the internal surface 

 of the anterior portion of the metapterygoid, and against the same surface of the adjoining portion 

 of the palato-quadrate cartilage. The larger mesial limb is a thin smooth and delicate, but relatively 

 large plate of bone, the ventral edge of the anterior portion of which lies in the groove on the dorsal 

 surface of the dorso-anterior limb of the ectopterygoid, and there rests against the inner surface 

 of the palatine bone and the same surface of the rod-like remnant of the palato-quadrate cartilage. 

 Posterior to the latter cartilage, the ventral edge of this plate rests against, and is bound by tissue 

 to, the internal surface of the metapterygoid. This mesial limb of the entopterygoid is closely applied 

 to the ventral surface of the anterior portion of the adductor arcus palatini muscle, and its dorso- 

 mesial edge is connected, by the lining menibrane of the mouth cavity, with the ventral surface of 

 the parasphenoid. 



The adductor arcus palatini has, as already stated, a long surface of origin, this surface be- 

 ginning on the lateral surface of the ascending process of the parasphenoid and on adjacent portions 

 of the proötic and from there extending forward along the lateral surface of the body of the para- 

 sphenoid as far as the antorbital cartilage. From this long surface of origin the broad muscle runs 



Zoologie«. Heft 57. 9 



