BONES FORMING OPERCULAR SERIES OF FISHES 65 



lucioceps; nine in Elops affinis and Harpodon microchir; ten in 

 Megalops atlanticus. The total number of branchiostegals is 

 three in the Cyprinidae and others, twenty-four to thirty-six in 

 the several species of Elops. Many other figures might be added, 

 but these are enough to illustrate clearly the inconstancy of the 

 number of branchiostegal rays in the generalized malacopterygian 

 fishes. 



In the groups of soft-rayed fishes other than the Isospondyli, 

 the jDranchiostegals are variable in form and attachment, but 

 they show many points of similarity to those of the Isospondyli. 

 In the Ostariophysi the number of rays varies widely, but the 

 uppermost, at least, remains like that of the isospondylous fishes. 

 To take several examples from the Nematognathi, there are six 

 branchiostegals in Arius gagora, seven in Pseudeutropius garna 

 and Saccobranchus fossilis, nine in Ictalurus punctatus, Amiurus 

 nebulosus and Shilbe mystus, eleven in Macrones aor. The 

 characins have only three to five branchiostegals, the cyprinids, 

 constantly three. This low number of branchiostegals in certain 

 malacopterygian fishes is usually correlated with the broad union 

 of the branchial membranes and with a fresh-water habitat. 

 Similarly, there are only three branchiostegals in Haplochiton, 

 Phractolaemus, Kneria, and Cromeria, and but four in the 

 Gonorhynchidae, Chanidae, and Salangidae (in all of these, 

 excepting Gonorhynchus,' the uppermost ray remains visible 

 below the margins of the opercles). In the Mormyridae and 

 Notopteridae the branchiostegals are modified in various ways, 

 as Doctor Ridewood ('04, pp. 191-195, 199, 205) has demonstrated; 

 in Notopterus there are six to nine branchiostegals, in Xenomystus 

 but three, according to Boulenger. 



The stomiatoid fishes, formerly confused with the Iniomi, have 

 the branchiostegals short, slender, little curved, evenly spaced, 

 not folded together, attached to the external surface of the hyoid 

 arch near its ventral edge (each opposite a photophore), and 

 largely covered by the opercula. In the Apodes (eels), Heteromi 



* In Gonorhynchus there are four branchiostegals, attached beneath the 

 opercles on the outer face of the club-shaped end of the hyoid arch, all above the 

 suture between the ceratohyal and epihyal. 



