Phthinobranchii | 443 
the two bones. In those species which have bony plates in- 
stead of scales, this bone has a deposit of bony substance or 
ganoid enamel at the surface. This gives it an apparent 
prominence as compared with other bones of the skeleton, 
but it has no great taxonomic importance. Dr. Hay 
unites the suborders Hemibranchii, Lophobranchit, and Hypo- 
stomides to form the order Phthinobranchiit (@6.vas, waning; 
Bpayyos, gill), characterized by the reduction of the gill-arches. 
These forms are really nearly related, but their affinities with 
the Percesoces are so close that it may not be necessary to form 
a distinct order of the combined group. Boulenger unites 
the Hemibranchtt with Lampris to form a group, Catosteomt, 
characterized by the development of infraclavicles; but we 
cannot see that Lampris bears any affinity to the stickle- 
backs, or that the presence of infraclavicle has any high 
significance, nor is it the supposed infraclavicle of Lampris 
homologous with that of the Hemibranchiit. The dorsal fin 
in the Hemzbranchiit has more or less developed spines; spines 
are also present in the ventral fins. The lower pharyngeals 
are separated; there is no air-duct. The mouth is small and 
the bones of the snout are often much produced. The preopercle 
and symplectic are distinct. The group is doubtless derived 
from some transitional spiny-rayed type allied to the Percesoces. 
The Lophobranchs, another supposed order, represent simply 
a still further phase of degradation of gills and ventral fins. 
Dr. Gill separates these two groups as distinct orders and 
places them, as aberrant offshoots, near the end of his series 
of bony fishes. We prefer to leave them with the other transi- 
tional forms, not regarding their traits of divergence as of any 
great importance in the systematic arrangement of families. 
The Sticklebacks: Gasterosteide. — The sticklebacks (Gaster- 
osteide) are small, scaleless fishes, closely related to the 
Fistulartide so far as anatomy is concerned, but with very 
different appearance and habits. The body often mailed, the 
dorsal is preceded by free spines and the ventrals are each 
reduced to a sharp spine with a rudimentary ray. The jaws 
are short, bristling with sharp teeth, and these little creatures 
are among the most active, voracious, and persistent of all 
fishes. They attack the fins of larger fishes, biting off pieces, 
