﻿ix. d, i Day: Ophiocephalus striatus 43 



side, except the 5th, which presents the left side and shows no 

 cartilaginous nodule. They lie opposite the corresponding inter- 

 haemal spines. 



VIII. BRANCHIAL APPARATUS 

 PLATES XV AND XVI 



Basibranchials (17). These are clearly illustrated in Plates 

 XV and XVI, in the former articulated, and in the latter dis- 

 articulated, but contiguous to those bones with which they are 

 articulated. 



The 1st is thickest at the posterior end, where it is not quite 

 as thick as wide. A slight ridge extends from the anterior to 

 the posterior end on the ventral side. 



The 2d is seen from the dorsal side, but, as the bone , is 

 rather deep, a profile drawing from the left side is shown in 

 text fig. 6. 



The 3d is about two-thirds as thick as broad, and has fossae 

 at the articulations of the hypobranchials (24) of the second 

 branchial arch and also at the posterior end. 



The 4th basibranchial has a shaft posteriorly, becomes thinner, 

 and just posterior to the middle widens out into 2 thin lateral 

 flanges. Anteriorly, it is broadly wedge-shaped. 



Hypobranchials (24) of the first arch. The outline of the 

 hypobranchials of the first arch is shown in Plate XVI, except 

 the epicondyle of the interior end. The dorsal portion of the 

 interior end articulates with the lateral fossa of the 3d basi- 

 branchial (17). The epicondyle passes to the ventral side of 

 the 3d basibranchial (17) and forward, articulating with the 

 posterior ventral portion of the 2d basibranchial (17). The 

 anterior process is almost lamellar. Laterally and distally these 

 hypobranchials articulate with the ceratobranchial (63). The 

 anterolateral margin is covered with small detachable plates of 

 cardiform teeth (133) which take the place of gill rakers. 



Hypobranchials of the 2d arch. These bones articulate distally 

 with the ceratobranchials (63). Proximally the articulation is 

 with the fossae of the 4th basibranchial (17), the posteroventral 

 margin of the 3d basibranchial, and with the anteroventral 

 process of the hypobranchials of the 3d branchial arch. They 

 are convex anterodorsally and concave posteroventrally. The 

 ventral anterolateral epicondyle is lamellar. The anterolateral 

 surface is covered with detachable plates of cardiform teeth. 



Hypobranchials of the 3d arch. The outline is clearly seen 

 in Plate XVI. Medially and posteriorly they articulate with 



