— 143 — 



aceording as the one bone or the other covcis the region; and tlie other, that the anterior palatine 

 process of the ethmoid needing support, a supporting plate is developed from the nearest bone 

 available. 



The FRU.M'AL has nearly straight mesial and hind edges, lying at a right angle to each other. 

 It has a small ventral flange, resembling somewhat, but much smaller than that of Scomber. Posterior 

 to this flange, on the ventral surface of the bone, there are two slight ridges, meeting at an angle, 

 which form, as the similar biit more developed ridges of Scomber do, the antero-mesial and antero- 

 lateral boundaries of the anterior end of the lateral cranial fontanellc. The frontal suturates mesially 

 with its fellow of the opposite side, posteriorly with the parieto-extrascapular, and laterally with 

 the pterotic, the postfrontal, and a small corner of the sphenotic that comes to the level of the outer 

 surface of the dermal bones. It is traversed by the supraorbital latero-sensory canal and lodges five 

 Organs of that canal, which are similarly disposed to those found in Scorpaena and Trigla; that is, 

 the second, third and fourth organs of the line are in regulär positions; the fourth and fifth organs lie 

 close together without intervening primary tube; and the sixth organ is a small one lying in the small 

 terminal tube of the line and innervated by a nerve that first issues in the orbit and then perforatcs 

 the alisphenoid to enter the cranial cavity and perforate the frontal beneath the organ it innervates. 



The POSTFRONTAL is a small bone that forms the roof of the small dilatator fossa, and is 

 bounded mesially by the frontal, posteriorly by the pterotic, and anteriorly by the dorso-lateral 

 corner of the sphenotic. It is traversed by the dorsal end of the postorbital portion of the main infra- 

 orbital canal, and lodges one organ of that canal, innervated by the ramus oticus lateralis. 



The PARIETO-EXTRASCAPULAR forms part of the hind edge of the secondary skull, and its 

 hind edge is thickened and grooved, as already described. The bone suturates anteriorly with the 

 frontal, and laterally with the pterotic, lateral extrascapular, and suprascapular, not overlapping 

 dorsally the epiotic process of the latter bone. It lies directly upon the supraoccipital, the epiotic 

 and the adjoining cartilaginous portions of the roof of the cranium, its lateral edge forming part of the 

 roof of the temporal fossa. Its hind edge is traversed by the supratemporal commissure of the latero- 

 sensory System and lodges one organ of that commissure. 



The LATERAL EXTRASCAPULAR is a small subcirculär bone lying between the fronto- 

 parietal and lateral spinous ridges, wedged in between the pterotic, parieto-extrascapular and supra- 

 scapular bones. It forms part of the roof of the temporal fossa, but does not come to the lateral edge 

 of the skull, being shut off from that edge by relatively wide suturating portions of the pterotic and 

 suprascapular. It is traversed by the lateral portion of the supratemporal latero-sensory commis- 

 sure and lodges one organ of that commissure. It is not perforated by the main infraorbital canal, 

 as in the other fishes described, the canal here simply passing along the lateral edge of the bone. 

 partly enclosed in it, and there apparently being no organ of the main infraorbital line related to it. 

 In this Peristedion resembles Dactylopterus, as will be later described. 



The SUPRASCAPULAR forms the postero-lateral corner of the dorsal surface of the skull, 

 and the larger part of the roof of the temporal fossa. It has a well developed opisthotic process, but 

 no differentiated epiotic process, that part of the bone that represents that process being relatively 

 short and appearing as an epiotic region rather than an epiotic process of the large body of the bone. 

 On the ventral surface of this epiotic region of the bone there is a small ventral process, and this 

 process and the adjoining portion of the mesial edge of the bone suturate with the hind end of the 

 suprascapular process of the epiotic. The anterior edge of this part of the bone suturates with the 



