PHARYNGEAL TEETH OF FISHES. 267 



teeth on the upper surface of the first four arches. There are 



two small groups of cardiform teeth on the heads of the third 



and fourth epibranchials for upper pharyngeal teeth. The 



lower pharyngeal teeth are in a long, narrow V shape of sharp 



cardiform teeth. The surface of the basibranchials has small 



cardiform teeth. 



Salmonid^;. 



Salmo solar (the Salmon) has thirteen short horny gill- 

 rakers on the first cerato-hypobranchial arch, with eight on the 

 epibranchial. The longest about a third the depth of the gill- 

 lamina below it. They all bear teeth. There are only three 

 minute gill-rakers on the inside of the first arch and these are 

 placed at the end near the tongue. The outer edges of the other 

 arches are furnished with similar but smaller gill-rakers to 

 those of the first arch. The second arch has five minute 

 gill-rakers on its inner side at the tongue end. The third and 

 fourth arches have them both sides all along. The upper 

 pharyngeal teeth consist of a very few small cardiform teeth 

 along the upper part of the third epibranchial, and rather more 

 and larger teeth on the upper part of the fourth epibranchial, 

 but even there these teeth are small. In neither case are they 

 arranged in such a dense group as is so common in other fishes. 

 The lower pharyngeal teeth consist of, similarly, a few cardiform 

 teeth, those nearest the oesophagus being fairly large. The 

 tongue has teeth on it. 



Thymallus vulgaris (the Grayling), an altogether fresh- 

 water member of the family, living in rivers, has twenty-two 

 long, thin, horny gill-rakers on the first cerato-hypobranchial 

 arch, with thirteen on its epibranchial. All these gill-rakers 

 are toothed. The longest is about half the length of the distance 

 from the angle to the junction with the basibranchials. They 

 decrease in size very quickly but very uniformly to each end 

 from the, angle. There are numerous thin horny gill-rakers on 

 the outer edges of the other branchial arches, but none of 

 them have gill-rakers on their inner faces. No pharyngeal teeth 

 could be made out in the specimen examined. 



Salvelinus willughbii (the Charr), from Lake "Windermere, 

 has fifteen moderately long horny gill-rakers on the first cerato- 

 hypobranchial arch with six on its epibranchial. The longest 



