PHARYNGEAL TEETH OF FISHES. 143 



gill-rakers on their outer sides, but situated low down, shorter 

 than those on the first arch, and getting shorter still from the 

 outer to the inner arches. The first and second arches have 

 none on their inner faces, but the third and fourth have. The 

 edge of the upper surface of the branchial arches is serrated. 

 The upper pharyngeal teeth show as two flattened spherical 

 patches of minute cardiform teeth, and the lower pharyngeal 

 teeth in two markedly broad triangular shaped surfaces, with a 

 distinct median division, are of similar but even finer teeth. 



Doras maculatus, the " Bombom " of Demerara, has twelve 

 short horny gill-rakers on the first cerato-hypobranchial, the 

 last three of which are rudimentary ; the longest one is at the 

 angle. The length of this is contained about two and a half 

 times in the depth of the gill lamina below it. There are three 

 gill-rakers on the first epibranchial. The other arches have 

 tubercle- shaped gill-rakers, which are set on the outer sides of 

 the arches and rather low down, and there are papillae on the 

 top surfaces of the second, third, and fourth arches, more 

 numerous on the latter two than on the second. A round- 

 shaped shield of villiform teeth attached to the third and fourth 

 epibranchials forms the upper pharyngeal teeth on each side. 

 The lower pharyngeals are in two distinct but roughly triangular 

 patches of villiform teeth. 



Synodontis schall, a Nile fish, has on the first cerato-hypo- 

 branchial arch seventeen horny gill-rakers, which are denticulated 

 on the inner side ; there are three on the epibranchial. The 

 second and third arches have a number of closely-set gill-rakers 

 covered with papillae. The mucous membrane lining the upper 

 part of the back of the mouth is covered with prominent papillae. 

 The upper pharyngeal teeth are in two circular patches, very 

 low down at the back of the mouth, with minute chocolate-brown 

 cardiform teeth. The lower pharyngeal teeth are in two diverging 

 patches, with two rows of prominent but small teeth standing up 

 along the inner edges of the patches, with smaller teeth outside 

 them ; these are likewise chocolate-brown in colour. It is inte- 

 resting to note that Gunther, in ' The Introd. Study of Fishes,'* 

 says of this fish: the teeth in the lower jaw "have a slightly- 

 dilated brown apex." 



:;; P. 573. 



