FISHES. 241 



the perch, or white perch. The scales are in this species also rather small, and the 

 teeth uniserial in each jaw, but it is distinguished from all the other members of the 

 family by the peculiar lower pharyngeal bones, that is the bones immediately behind 

 the gill arches ; these are very large, behind convex, and sloping downwards, with the 

 anterior teeth truncated and tessellated, and the posterior flattened, imbricated, and 

 pi'essed forwards. The species attains a weight of about two and a half or three 

 pounds. It ranks as second to the alfiona as a food fish. 



Two other species, congeneric with the Japanese fish, are known as the black surf- 

 fish, and reach a weight of from two to two and a half pounds. One of these, 

 Ditrema lateralis, is " an important food fish, although not of very good quality ; " 

 while the other, D. jacksotii, is probably brought into San Francisco market "in 

 greater numbers than any other species," although it is " an indifferent food fish." 



Perhaps the most abundant of all the surf-fishes is the little Cymatogaster aggre- 

 gatus, which is generally known as shinei*, but on Puget Sound is called minny, and 

 by the Italians of California, sparada or sparad. All the preceding species feed upon 

 crustaceans, or such small fishes as they can take, but there is one species peculiar in 

 its diet. The Abeoiia aurora is distinguished by a peculiarity in dentition concomi- 

 tant with a peculiarity in food. It is said to feed upon sea plants or algae. It reaches 

 a weight of about a quarter of a pound. 



The surf-fishes are all inhabitants of the sea, save one species, which is confined to 

 fresh water. The liysterocarpus traski, which is known as the river perch, is a 

 species distinguished by the great extent of the spinous portion of the dorsal fin, which 

 is longer than the soft, and composed of sixteen to eighteen spines. The scales are 

 large, and the teeth conical and uniserial. It reaches a weight of about half a pound. 

 It is only found in the Sacramento and San Joaquin Rivers, and other streams of Cali- 

 fornia as far southward as San Luis Obispo. " It is sent in small numbers to the 

 markets of San Francisco, and is chiefly eaten by the Chinese." 



One of the most remarkable groups of fishes has its headquarters in India, though 

 a few species are found in Africa. Their peculiarity is chiefly exhibited in the com- 

 plication of the pharyngeal bones and the contiguous parts. In allusion to this compli- 

 cation the group was long ago called by Cuvier the fishes with labyrinthiform 

 pharyngeals. 



The upper elements of one of the pairs of the gill-bearing arches are peculiarly 

 modified. The elements in question (called branchihyal) of each side, instead of being 

 straight and solid, as in most fishes, are excessively developed and provided with 

 several thin plates or folds, erect from the surface of the bones and the roof of the 

 skull, to which the bones are attached. These plates, by their intersection, form 

 chambers, and are lined with a vascular membrane, which is supplied with large blood 

 vessels. It was formerly supposed that the chambers referred to had the ofiice of 

 receiving and retaining supplies of water which should trickle down and keep the gills 

 moist ; such was supposed to be an adaptation for the sustentation of life out of the 

 water. The experiments of Surgeon Day, however, throw doubt upon this alleged 

 function, and tend to show, (1) that these fishes died when deprived of access to 

 atmospheric air, not from any deleterious properties either in the water or in the 

 apparatus used, but from being unable to subsist on air obtained solely from the water, 

 aerial respiration being indispensable ; (2) " that they can live in moisture out of the 

 water for lengthened periods, and for a short but variable period in water only ; " and 

 (3) that the cavity or receptacle does not contain water, but has a moist secreting 



VOL. III.— 16 



