44 THE DISCOBOLI. 



absent in some species. Caudal fin elongate, distinct, or united with dorsal 

 and anal. Anal and dorsal long, the latter rarely with the portion con- 

 taining spinous or unsegmented rays distinct from the other. Skin smooth, 

 excepting a sexual outgrowth in breeding season, thin, not firmly attached. 

 Vessels of the lateral system cephalic. Olfactory nerves short. Stomach 

 siphonal, U-shaped, with caeca. Intestine elongate. 



Skeleton with a somewhat larger proportion of osseous matter than 

 that of the Cychpteridce. As in that family, the skull is full on the back, 

 as if truncate, and has no passage for muscles extending forward between 

 the mastoid and the occipitals. Third suborbital very long, slender, and 

 spine-like, posteriorly reaching toward the posterior margin of the pre- 

 operculum. Upper limb of preoperculum expanded. Operculum much 

 reduced ; its shape with some resemblance to that of a boot, the sole 

 directed down and the toe backward. Suboperculum slender, like an in- 

 verted V with the limbs curved outward, the anterior extending forward 

 along the preoperculum, and the posterior reaching back under the lower 

 border of the operculum. Interoperculum long, styliform, reaching from 

 suboperciilum to articular, frequently mistaken for one of the branchios- 

 tegal rays. 



Between the members of this family and other Discoboles prominent 

 distinguishing features are seen, in the shorter body as compared with 

 the caudal sections, the greater number of vertebrae, the peculiarities of 

 the fins, and the development and shapes of the opercular bones. 



Reasons for separating this family from the Cyclopteridae and placing 

 it farther from the Cottidoe exist in the continuous dorsal, the connection 

 of dorsal and anal with the caudal, the more complete transformation of 

 the ventral rays, the more slender and spine-like suborbital process, the 

 expanded upper limb of the preoperculum, the styliform interoperculum, 

 the shorter olfactory nerves, and the more elongate brain. 



