No. 2.] MORPHOLOGY OF THE MYXINOIDEI. 207 



anterior arch. The posterior arch does not support any teeth. 

 The tendons of the retractor, as well as the protractor, muscles 

 are attached, not to the cartilages directly, but to the strong 

 fibrous membranes which surround them. 



The foregoing description has included the skeletal parts 

 making up the dorsal and ventral portions of the skull and 

 the cartilages of the mouth region. The lateral walls of the 

 skull, especially in the posterior region, are supported by a 

 framework of cartilages (" Schlundkorb " of Johannes Miiller). 

 A comparison of Figs. 5, 6, and 7 will show that this frame- 

 work is, for the most part, composed of a number of vertical 

 arches, connected on each side by two longitudinal bars, a 

 dorsal and a ventral. The cartilages of this framework, as we 

 shall see, are really metamorphosed visceral arches. Begin- 

 ning anteriorly, we find the latbral walls of the skull, in front 

 of the auditory capsules, and external to the trabeculae, sup- 

 ported by the heavy irregular palato-pterygo-qnadrate bars 

 (Plate XXII, Figs. 5, 6 ; Plate XXIII, Fig. 7, PQ, PL). The 

 palato-pterygo-qtiadrate on each side has two main divisions — 

 an anterior, the palatine bar, and a posterior, the pterygo- 

 quadrate cartilage, PQ. The palatine bars (Figs. 5, 6, 7, PI) 

 are a pair of large, strong, cartilaginous rods, extending along 

 either side of the nasal capsule and the posterior fourth of 

 the nasal tube, at about the level of the floor of the latter. 

 The olfactory capsule and nasal tube rest upon the flattened 

 surfaces of the palatines, which look upward and inward, but 

 there is no cartilaginous connection between them. Anteri- 

 orly the palatine bars converge slightly toward the median 

 line. Finally they turn abruptly toward each other and are 

 connected at the anterior end by a short, broad, flattened trans- 

 verse commissure (Fig. 7, an) which faces upward and slightly 

 forward. To the inner margins of the palatines, a short distance 

 behind the commissure, are attached the anterior processes 

 of the hypophysial plate. On the upper surface of the com- 

 missure, in the median line near the posterior margin, is 

 attached the posterior end of the subnasal cartilage. At the 

 anterior external angles are attached the posterior ends of the 

 cornual cartilages, as previously mentioned. At the posterior 



