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similar process is found on the preniaxillary, there lying immediately external to and covering the 

 antero-mesial end of the maxillary; and this must be the articiilar process of the bone, if that process 

 is not represented in bone 2 of Huxley's descriptions. 



The articular process of the premaxillary of teleosts would thus seem to be as early, or even 

 an earlier acquisition of that bone than the ascending process. This has led me to reconsider the 

 conditions found in Amia, in which fish there is, as is well known, a large posterior process of the 

 premaxillary, but no ascending process. This posterior process I was led, in an earlier work ('98), 

 to consider as an olfactory sensory ossicle fused with the premaxillary, this conclusion being largely 

 based on a description of, Gymnarchus that I have since found to be erroneous (AUis, '04). My present 

 work leads me to consider it as a greatly developed articular process of the premaxillary: for the 

 maxillary articulates with its postero -ventral surface (Allis, '98), as it should, and its relations to the 

 nasal sac are such as might be readily acquired by a posterior prolongation of the process of Scorpaena. 



R S T R A L. 



The rostral is a median piece of cartilage, longer than it is tall, and about as tall as it is broad. 

 Its external, or dorso-anterior surface, which is slightly concave, gives support and attachment, on 

 either side, to the ascending process of the corresponding premaxillary. Its internal, ventro-posterior 

 surface is considerably wider than the external one, and is grooved its full-length, in the median line, 

 the groove fitting upon and sliding backward and forward upon the median internasal ridge. A short, 

 stout ligament arises from the side of the rostral, and running downward and backward, is inserted 

 on the mesial surface of what I shall describe as the ascending process of the maxillary, near its ventral 

 edge. From the posterior half of the latero-ventral edge of the rostral, and in part, also, from its 

 ventral surface, arises a tough fibrous or ligamentous band, which is in part inserted on the pointed 

 mesial (proximal) end of the maxillary and in part on the shank of that bone. In that part of the 

 band that has this latter Insertion is suspended the semi-cartilaginous nodule that is interposed bet- 

 ween the articulating surfaces of the vomer and maxillary. 



In Gasterosteus, according to Swinnerton, the rostral is a chondrification, in late stages of 

 development, of a mass of densely nucleated tissue, which, in earlier stages, lies chiefly on the under- 

 side of the ascending processes of the premaxillaries. In Salmo, Gaupp ('03) finds the rostral arising 

 in exactly the same manner, and as he had not apparently noticed Swinnerton's description he con- 

 siders the discovery of this development of this cartilage in Salmo as a support to the assumption 

 that the premaxillary is a dermal bone developed in relation to a labial cartilage. But if the ascending 

 process of the premaxillary is not primarily a part of that bone, as I maintain, the cartilage would 

 seem not to have this special significance. In any event the rostral is quite certainly not a detached 

 portion of the primordial cranium. 



MAXILLARY. 



The maxillary is a curved untoothed bone, with a flat, expanded hind end, and a somewhat 

 complicated anterior end. This latter end of the bone forms its articular head, and may be said to 

 bear two plate-like processes of bone, so placed as to give to the end of the bone a broad and some- 

 what V-shaped appearance. The antero-mesial (proximal) end of the shank of the bone curves rather 

 sharply mesially and lies directly above the dorsal limb of the vomer, but it is apparently not in sliding 



