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The terni „posterior", used by Sagemehl to describe the relations of the maxillary to the pre- 

 maxillary, is confusing; for while the articular end of the maxillary certainly lies posterior (internal) 

 to the premaxillar}', the shank of the bone, in all the fishes of which I have specimens, lies dorso- 

 external (that is, anterior or lateral, as the case may be) to the shank of the premaxillary, this relation 

 of the bones being particularly marked when the shank of the premaxillary has a certain dorsal process 

 which I shall describe as the post-maxillary process of that bone. 



The dorsal limb of the vomer of teleosts forms an anterior portion of the more or less developed 

 internasal wall, and it is of membrane, or perhaps partly of perichondrial origin. It accordingly does 

 not present the only two conditions that I formerly ('98, p. 458) found unfavourable to the homo- 

 logization of the preethmoid (septomaxillary) of Amia with the vomer bone of mammals. 



P A R A S P H E N I D. 



The parasphenoid of Scorpaena is a nearly straight bone, with well developed ascending pro- 

 cesses near the middle of its length. It has a rounded anterior, and a bifurcated posterior end, and 

 the anterior portion of its ventral surface is grooved, as usual, to receive the posterior portion of the 

 body of the vomer. Anterior to its ascending process there is, on the dorsal surface of the bone, a 

 thin longitudinal median ridge which fits into a corresponding depression on the ventral surface of 

 the chondrocranium. Beginning immediately posterior to the ascending processes, there is also, on 

 the dorsal surface of the bone, a median longitudinal ridge, but this ridge is broad and is grooved on 

 its dorsal surface. Anteriorly this groove is shallow, but posteriorly it deepens gradually, until, near 

 the bind end of the bone, it cuts through it, leaving only two pointed processes, one on either side. 

 The groove forms the median part of the floorof the myodome (eye-muscle canal), the ridge lying be- 

 tween the ventral ends of the proötics, and the cartilage that caps those bones abutting, on either side, 

 against its lateral surface. 



Swinnerton says ('02, p. 532) that, in Gasterosteus, the ascending process of the parasphenoid, 

 on either side, lies anterior to the exit of the trigeminus nerve, and that it meets and overlaps a process 

 of the frontal sent down immediately in front of the sphenotic. Because of this position, anterior to 

 the trigeminus foramen, he concludes that the process in Gasterosteus can not be the homologue of 

 the similarly named process in Amia, in which fish it lies posterior to the trigeminus foramen, This 

 conclusion is partly correct and partly incorrect, for the bases of the ascending processes, in the two 

 fishes, are homologous, while the dorsal prolongations of those basal portions are not. The entire 

 process lies, in Scorpaena and Scomber, ventral to the trigeminus foramen, and this would seem to 

 be the usual teleostean relation. In Amia, a dorsal Prolongation of this basal portion of the process 

 passes posterior to the trigeminus foramen, comes into contact with the sphenotic, and seems to be 

 in some way related to the spiracular canal. In Gasterosteus, a dorsal Prolongation of the basal 

 portion passes upward anterior to the trigeminus foramen, there invading and taking possession of 

 the region occupied, in Amia, by the so-called pedicle of the alisphenoid, which latter bone is said 

 by Swinnerton to be absent in Gasterosteus. This arrangement of the parasphenoid, in Gasterosteus, 

 is apparently exactly similar to that found in Cottus, where the process of the bone comes in contact 

 with the alisphenoid as well as with the ventral flange of the frontal, as will be fully described when 

 describing that fish. Here it need only be said that that part of the alisphenoid of Amia that has 

 been described as the pedicle of the bone, is largely or even wholly absent in certain teleosts, there 



