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part of the dorsal surface of the skull. The postfrontal forms part of the roof of tlie dilatator fossa, 

 bears two or three short blunt spines, and is traversed by the main infraorbital latero-sensory canal, 

 lodging one organ of that canal, innervated by the ramus oticus lateralis. 



In Scorpaena porcus, the postfrontal is a short, small, tubulär bone, and bears but one, or at 

 most two spines. 



PARIETO-EXTRASCAPULAR. 



The parieto-extrascapular is formed by the fusion of the parietal with the mesial ossicle of the 

 extrascapular latero-sensory series. This fusion, in certain other fishes, of these two usually separate 

 elements was fully discussed by me in a recent work ('04). As further confirmation of the fusion, 

 the conditions in Chanos can be cited, where, according to Ridewood ('04a, p. 58), „the parietals are 

 widely separated in the young but by subsequently fusing with the scales of the commissural section 

 of the sensory canal System, they come to meet above the supraoccipital bone". 



In Scorpaena, the parieto-extrascapular is a relatively large and very irregulär bone, with a 

 much ridged dorsal surface. One of these ridges is the parietal spinous ridge, which has already been 

 described. Another and lower ridge lies immediately lateral to the parietal ridge, is formed, anteriorly, 

 by the lateral bounding ridge of the groove on the vertex, and, posteriorly, by the nuchal spinous 

 ridge; the ridge being interrupted between these two portions. Immediately lateral to this ridge, 

 there is a curved ridge, tall in its middle portion but low at either end, the hollow of the curve presented 

 laterally. The posterior portion of this ridge marks the course of a part of the supratemporal latero- 

 sensory canal. A mesially projecting corner of the bone lies on the posterior portion of the dorsal 

 surface of the supraoccipital, articulates by suture, usually serrate, with its fellow of the opposite 

 side, and forms the summit of the ridge that bounds posteriorly the groove on the vertex. A large 

 reentrant angle at the postero-lateral corner of the bone receives the antero-mesial corner of the 

 lateral extrascapular, the edges of this part of the parieto-extrascapular overhanging slightly the 

 temporal fossa and forming part of its roof. 



The posterior half of the parieto-extrascapular is a stout, broad process-like portion which 

 projects postero-laterally and lies slightly dorsal to the dorsal surface of the suprascapular process of 

 the epiotic; the narrow space between itself and that process of the epiotic receiving the epiotic arm 

 of the suprascapular. From the internal surface of this part of the bone, near its hind edge, a delicate 

 Hange projects ventro-posteriorly. The antero-ventral surface of this flange lies upon that part of 

 the dorsal surface of the epiotic that lies immediately anterior to the base of the suprascapular process 

 of that bone. The postero-dorsal surface of the flange forms part of the floor of the supratemporal 

 pocket and thus forms part of the apparent posterior surface of the adult skull, but it lies on a part 

 of the dorsal surface of the primary skull, and not on its posterior surface, as already explained. 



The anterior half of the parieto-extrascapular rests in part upon the dorsal surface of the 

 pterotic and supraoccipital, in part upon remnants of the chondrocranium adjacent to those bones, 

 while, in part, it bridges the lateral fontanelle of the skull, there forming part of the roof of the cranial 

 cavity. The anterior edge of the bone articulates by suture with the hind edge of the frontal, the 

 mesial edges of the parieto-extrascapulars not here meeting in the middle line, and a median portion 

 of the supraoccipital being exposed between them. The bone is traversed by the supratemporal 

 latero-sensory canal, the canal usually lodging a single sensory organ, but in one specimen this organ 

 had apparently separated into two parts, lying close together. In 45 mm specimens there is but a 



