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connection. Eegarding bone 2 of Esox I have made no further investigation, but it would certainly 

 seem to be the homologue of the dermal ethmoid of Amia. 



In Lophius piscatorius, the premaxillary has a well-developed articular process, but no at- 

 tacbed ascending process. At the place where this latter process would normally arise, there is a 

 transverse facet which gives articulation to the anterior end of a long and tapering bone. This is 

 all seen in Bruhl's ('56) figures of this fish, and the long and tapering bone is considered by that author 

 as the detached ascending portion of the premaxillary (infra-maxillarv), which it unquestionably is. 

 It lies close against its fellow of the opposite side, the two bones, united, lying in a large rostral 

 Chamber on the dorsal surface of the snout. No rostral cartilage is found, but it is quite unquestionably 

 represented in the tissues that envelope and underlie the two bones. The ascending processes of 

 the premaxillaries thus here have a shape and position that render them easily recognizable as 

 those processes, which the dermal ethmoid bones of Amia and Esox have not, and yetf as in these 

 latter fishes, the two bones are wholly independent of the bodies of the premaxillaries. 



In Sphyraena vulgaris the premaxillary has both articular and ascending processes. The 

 ascending process rests against the antero-mesial edge of the articular process, wholly free from it, 

 but flexibly and apparently uninterruptedly connected with the premaxillary immediately antero- 

 mesial to the base of the articular process. The connection is by the intermediation of what looks 

 like gristly tissue, and it is evident that a primarily independent bone is here in process of fusion 

 with the premaxillary. That the bone can not be an outgrowth of the premaxillary that is in process 

 of becoming detached from it, seems self-evident. 



In Salmo salar, Parker ('73) shows the premaxillary as a large and somewhat triangulär bone, 

 the point of the triangle directed dorso-posteriorly and overlapping the proximal end of the maxil- 

 lary. At the mesial edge of the bone a short process is shown which might, in the figure, be consi- 

 dered as an ascending process. This is, however, probably an error in the drawing, for I have exani- 

 ined both Salmo trutta and Christivomer namaycush and do not find the process in either. The 

 premaxillary bone, in both these latter fishes, is somewhat triangulär, as shown by Parker in Salmo 

 salar, but the dorso-posteriorly directed point of the triangle lies near the middle of the length of 

 the bone and not at its mesial edge, as an ascending process should. The process, moreover, over- 

 laps the proximal end of the maxillary, and gives articulation, on its internal surface, to that bone. 

 It is accordingly a part of the articular process of that bone and not an ascending process. And in 

 all of these three fishes there is an independent so-called supraethmoid. 



In Elops saurus the maxillary has the relation to the premaxillary that is designated by Sage- 

 mehl as lateral. The premaxillary is without ascending process, and articulates, by its antero-mesial 

 end, with the antero-lateral edge of a bone that Ridewood f04.a) considers as a mesethmoid firmly 

 united with a vomer. This mesethmoid bone of Elops is said by Ridewood to be separable without 

 much difficulty into two components, „the upper part (supraethmoid of some authors) being a mem- 

 brane bone, while the lower part, of diminutive size is a cartilage bone". In my two specimens of the 

 fish this membrane component of the mesethmoid bone is traversed by a cross-commissural canal 

 which is in communication, at either end, with the infraorbital latero-sensory canal. It was not 

 possible to establish the presence of sense organs in this canal, but it is, nevertheless, quite unques- 

 tionably the homologue of the anterior or ethmoid commissure of the Crossopterygü and Ganoidei 

 Holostei (Allis, '04), and it has never heretofore been found in any teleost. The infraorbital canal, 

 after having traversed the anterior one of the circumorbital bones shown in Ridewood's figures. 



Zoologica. Heft 57. 4 



