THE PHARYNGEAL TEETH OF FISHES. 187 



" Pirarucu " at Manaos on the Amazon, where it is caught 

 in large numbers. This fish is the largest of fresh-water fishes, 

 and said to grow to twelve feet in length ; portions of one 

 five feet nine inches in length were obtained. The basibranchials 

 at the base of the tongue have a bony structure covered with 

 small conical teeth set very closely together ; it is eight inches 

 in length by one and five-eighths inches in breadth in the centre. 

 One end is rounded, the other terminates in a narrow ellipsoid 

 shape ; at this end the teeth disappear or become so minute as not 

 to show as teeth, leaving the surface, however, very rough. This 

 bone is used by the natives of the country where the fish is caught 

 as a grater. On the parasphenoid, under the skull and above the 

 " grater " bone, there is a group of similar teeth of an elongated 

 oval shape, which is some five inches long and one and two-fifths 

 inches wide, at its widest, of closely-set, palpable teeth, which 

 then continue as a narrow band to the vomer. These fishes have 

 no pharyngeal teeth, but those described above supply an efficient 

 masticatory arrangement in their default. 



Clupeid^. 



This family, to which the Herring belongs, supplies a large 

 number of excellent fish for the table. 



Clupea finta, the Twait Shad, has twenty to twenty-one long, 

 horny gill-rakers on the cerato-hypo- of the first branchial arch ; 

 the first ten from the angle keep much of a size, and are in 

 length equal to the depth of the gill-laminae below them. In one 

 specimen examined there were twelve on the right epibranchial 

 and nine on the left one. All the gill-rakers are smooth. 

 Pharyngeal teeth, upper and lower, are wanting. The other 

 branchial arches carry similar long gill-rakers on their outer 

 sides only. These long gill-rakers make a good filter for the 

 mouth (fig. III., 2). 



Clupea harengus, the Herring, has forty-two long, fine, horny 

 gill-rakers on the cerato-hypo- of the first branchial arch ; they 

 are serrated on the inner edge. In length the longest one, 

 near the centre of their number, is one half as long again as 

 the gill-laminae below it. The forty-two are contained in a 

 length of one and three-sixteenths of an inch, so that approxi- 



