569 



bones of the roof of the skull, as in Scomber. In the mail-cheeked 

 fishes, these anterior extensions are not found, but the areas occupied 

 by them in Scomber are represented, on either side of the dorsal sur- 

 face of the skull of the Loricati, by contiguous regions bounded by 

 four more or less developed ridges that radiate approximately from the 

 frontal spine. 



The temporal fossa may have an epiotic diverticulum, and it may 

 also have, as in Amia, an anterior diverticulum. This latter diverti- 

 culum lies on the. dorsal surface of the primary cranium, beneath the 

 dermal bones of the roof of the skull, and in certain fishes (Elops, 

 Albula) it becomes a large and important portion of the fossa. But 

 this anterior diverticulum of the fossa must not be confounded with 

 the anterior extension just above referred to, the former lying ventral 

 and the latter dorsal to the dermal bones. 



The anterior extensions of the supratemporal grooves have coal- 

 esced in the Loricati to form the subquadrangular groove on the vertex. 



3. The premaxillary of the mail-cheeked fishes has, on its proximal 

 end, two processes, one of which is the ascending process properly so- 

 called and the other an articular process ; but the two processes together 

 are usually referred to as the ascending process of the bone. 



The articular process is probably the earlier acquisition of the 

 two, is apparently found in all osseous fishes, and it, alone, is some- 

 times miscalled the ascending process of the bone (Amia, Salmo). 



The ascending process is formed by the fusion with the pre- 

 maxillary of a supraethmoid bone, the latter bone being primarily 

 developed in protective relation to a line of latero-sensory organs, 

 and being so found, not only in certain ganoids (Amia, Polypterus) 

 but also in Elops and probably in Belone, these two teleosts being 

 the only ones in which it has as yet been found. In Belone the bone 

 is indistinguishably fused with the premaxillary, while in Elops it is 

 found as an independent ossicle. 



4. The maxillary of the mail-cheeked fishes has, on its proximal 

 end, a process that may be called its ascending process. This process 

 gives articulation to the articular process of the premaxillary, and 

 itself articulates, by the intermediation of a pad of semi-cartilaginous 

 tissue, with the dorsal surface of the ascending process of the vomer. 

 This process of the maxillary is apparently found in all the Acantho- 

 pterygii and Anacanthini of Günther's classification, but it is not 

 evident in all descriptions of the Physostomi. In those fishes in which 

 it is found it varies greatly in its development, and may even be found 

 as two instead of as a single process. 



