392 TRANSACTIONS OF THE AMERICAN PHILOSOPHICAL SOCIETY 



hinge-like articulation for the second vertebra, which, at least in Histrio, is bent downward 

 at a sharp angle, as the column curves down and around the expanded body cavity. The 

 neural arches of the first vertebra are expanded anteroposteriorly and stiffened posteriorly. 

 At the base they are excavated to receive the lateral exoccipital condyles. They diverge 

 gently at the top but are connected above across the top by a thin chevron, which may 

 represent a modified epineural bone. 



The base of the cranial vault is formed in the rear by the ventrally stiffened basiocci- 

 pital, which narrows into a half-tube posteriorly but broadens anteriorly to hold the otoliths 

 and to make contact with the posteriorly flaring parasphenoid. The keel of the latter is 

 narrow but greatly stiffened to receive the thrusts from the large transversely widened 

 vomer and from the prefrontals. The lateral ascending processes of the parasphenoids are 

 short; they are appressed to the prootic but, according to Tate Regan (1912/, p. 282) they 

 do not reach upward to the frontals as they do in Lophius. 



Thus as a whole the neurocranium of Antennarius has a broad, rather stoutly-braced 

 cranial vault and a large stiff parasphenoid keel supporting the very wide vomer; the slender 

 interorbital region has raised orbital rims and a deep median V-shaped depression containing 

 the large ascending and articular processes of the premaxillae. The mesethmoid, which 

 forms the bottom of this deep depression, is reduced in the side view to a curved rod with an 

 expanded lower end and in the top view to a V with a long anterior tip. The median depres- 

 sion formed by the supraoccipital and the frontals is more or less filled by the basal rods of 

 the second and third dorsal rays and their attached muscles. 



It has already been shown how variously the neurocranium has been affected by the 

 cavernous development of the jaws, mouth and throat; but the detailed interrelations of the 

 various parts of the branchiocranium remain to be described. The excessive depression 

 of the quadrate-articular joint and the enlargement of the gullet have involved the marked 

 vertical elongation of the hyomandibular, of the quadrate, preopercular, inter- and sub- 

 opercular, cleithrum, supracleithrum and branchiostegals. The space between the hyo- 

 mandibular and the shoulder-girdle being very narrow in proportion to its height, the 

 opercular is correspondingly narrow; it is also thin and membranous, the opaque bony parts 

 being reduced to two forking streaks, including a much larger anterior branch, which is 

 nearly vertical, and a much more delicate short posterior branch, the two meeting above and 

 overlapping the large opercular pedicle of the hyomandibular. The anterior pointed lower 

 tip of the opercular is received between a small fork of the subopercular; this fork has a 

 short anterior and a much longer and broader posterior branch; from the notch the sub- 

 opercular continues downward and forward as a somewhat dagger-like blade with a curved 

 posterior border; it is closely appressed to the lateral face of the longest and largest bran- 

 chiostegal. In the rear view the opercular is bowed outward beyond the straight cleithrum 

 so that the posterior border of the opercular is no longer flush with the lateral surface of the 

 cleithrum, as it is in the majority of fishes; thus in the dried skeleton the gap between the 

 opercular and the cleithrum remains permanently open. In life, however, this gap is 

 covered laterally by the skin that forms the tube leading to the functional spiracle, behind 

 and above the pectoral fin. 



The preopercular is a thin vertically deep bone fastened tightly to the lateral crest of 

 the hyomandibular and to the posterior ridge of the quadrate; it stiffens the long suspen- 

 sorium. Posteriorly it covers the long sliver-like interopercular, which as usual is attached 



