352 CALIFORNIA ACADEMY OF SCIENCES. 



a terminal barbel which is partly united with the oval 

 disk; no mental or nasal barbels. Teeth, if present, 

 hooked and usually two-lobed at the tip; the active ones 

 in a single series; intermaxillaries separate from each 

 other, box-shaped and filled with numerous relay teeth, 

 dentaries separate from each other and constructed like 

 the intermaxillaries. No teeth on the palate; no fron- 

 tal or occipital fontanels. Dorsal fin present, situated 

 on the abdominal portion of the vertebral column, and 

 not connected with the occipital by processes. Adipose 

 fin, if present, composed of a spine, and a thin mem- 

 brane. Anal fin short. Gill-membranes joined to the 

 isthmus, the gill-openings restricted to the sides. In- 

 testinal canal elongate, coiled upon itself. 



Nares close together, a flap between them, little above 

 and in front of the eyes. Iris with a flap encroaching 

 on and sometimes entirely dividing the pupil. 



Caudal vertebrae compressed, the neural and hoemal 

 spines expanded, forming a continuous ridge above and 

 below. 



Air-bladder cavity narrow at the base and expanded 

 beneath the temporal plate, usually communicating with 

 the exterior at a notch in the posterior margin of the 

 temporal plate, in Otocinclus and Microle'pdogdster by many 

 holes in the temporal plate. 



Strong movable bones, (ribs ?) extend from near the 

 posterior end of the coalesced vertebrae outward. They 

 are compressed and widened at the base. In the Piecos- 

 tomince they are forked at the base, the lower branch 

 articulating with the centrum of the vertebra, the upper 

 branch with the middle of the neural spine. In the 

 Loricariimv (Loricaria hvviuscida) their base is truncate 

 and touches the vertebra from the lower margin of the 

 centrum to the middle of the neural spine. Externally 

 these '' ribs " articulate with a more or less paddle-shaped 



