SALMONOJDS. 143 



which cross obhquely the angle of the mouth, are directed forwards. 

 In the genus Saurus, the mouth presents the anomalous condition 

 among fishes of edentulous intermaxillaries, with a formidable array 

 of teeth in the upper jaw, supported exclusively by the superior 

 maxillary bones ; these meet at the middle line, and the small inter- 

 maxillaries, which are recognizable by their characteristic ascending 

 process, are placed above and parallel to the median extremities of 

 the maxillary bones ; the teeth are slender, conical, and very acute ; 

 they are arranged in three or four rows, and form conical groups, with 

 the longest tooth in each placed innermost ; these teeth have their 

 apices slightly expanded. Similar spear-shaped teeth are arranged on 

 the premandibular bones below ; and likewise crowd the palate, 

 the tongue, the branchial arches, and the upper and lower pharyn- 

 geals. 



The disposition and usual form of the teeth in the typical genus 

 Salmo are represented in a diminished view of them in the common 

 salmon, as seen in looking into the cavity of the open mouth, (PL 

 48, fig. 9). The teeth all present the same simple form, short, 

 stout, pointed, and incurved ; from four to five are implanted in each 

 intermaxillary bone, the remainder of the single row which arms the 

 upper margin of the mouth, being supported by the superior maxillary 

 bones. In the young salmon there are two or three teeth on each 

 side of the anterior part of the vomer ; but, as growth proceeds, they 

 are reduced in number, and finally disappear in aged fish ; each 

 palatine bone supports a single row of teeth, nearly parallel with, 

 but smaller than, those of the maxillary rows ; there is a single row, 

 on each premandibular bone ; and a double row united by a crescent- 

 shaped series on the anterior part of the tongue. The pharyngeal 

 bones are armed w4th similar teeth. 



The principal difference observable in the allocation of the teeth 

 in the species of Salmo obtains in the vomer ; upon which, in the 

 salmon-trout and common trout(l) for example, the teeth are extended 

 backwards in a row, and deeply indent the surface of the tongue 

 between the two lateral rows of lingual teeth. 



The teeth are anchylosed by their bases to the several dentigerous 



(1) Mr. Yarrell has given a figure of the dentition of the common trout in vol. ii, p. 3, of 

 the British Fishes. 



