Food Relations of Fresh- Water Fishes. 507 



commonly opposed by superior pharyngeals, which most fre- 

 (^uently consist of osseous and cuticular thickenings of the 

 upper ends of the gill arches, — sometimes of only one or two, 

 as in the catfish family, sometimes of all, as in the sunfishes. 

 In the cy]irinoids, the upper pharyngeal is a (juadrate or tri- 

 angular pad, rarely, if ever, toothed, borne upon an oblique, 

 expanded process of the basioccipital. In the sucker family 

 the sickle-shaped lower pharyngeals act against a more or less 

 indurated palatal arch supported by the same cranial process, 

 the firmness and width of this hardened band varying with the 

 development of the lower arches of the apparatus. In most 

 of the Acanthopteri and in the catfish family the lower pharyn- 

 geals have a fusiform outline, varying in width according to 

 the food, the upper surface set with minute denticles, sharp- 

 pointed in the insectivorous species, more or less blunt and 

 conical in those which take a considerable percentage of mol- 

 luscan food. The immense development of these structures in 

 the sheepshead ( Aplodinotus), as a crushing apparatus for 

 Mollusca, is too well known to require description. In the 

 CatostomatidiU the number of teeth may vary from thirty or 

 less to two hundred or more, reduction in number going with 

 increase in size (especially in the lower part of the arch,) 

 both being related to an increased importance of molluscan 

 food. 



In the cyprinoids or minnow family, this is practically an 

 insectivorous apparatus, except in some of the species with very 

 long intestine and the limophagous habit, where it seems useful 

 chierty as a means of grinding up the mud ingested. 



In the piscivorous species, and in those with highly devel- 

 oped gill-rakers, the lower pharyngeals are commonly slight and 

 insignificant; but in the former group the upper pharyngeals 

 may be preserved and enlarged as a basis for the insertion 

 of hooked teeth, to aid in the retention of their struggling 

 prey. 



Concerning the digestive structures, I will only remark 

 that the fishes with the longest intestine are mud-feeders, as a 

 rule, and that in one of them, — thegiz/ard shad, a mud lover, 

 par excellence, — the pharyngeal jaws (which in the mud-eating 

 cyprinoids are evidently used to grind the food) are function- 



