XXI OSTARIOPHYSI 581 
a distance, but this faculty is exhausted by continuous employ- 
ment, and is recovered during repose. Although apparently 
not exempt from exaggeration and fable, Humboldt’s account in 
Observations de Zoologie, p. 497, is recommended for further 
information on the habits and modes of capture of Gymnotus.' 
Fam. 3. Cyprinidae.— Mouth usually more or less protractile, 
toothless, bordered by the praemaxillaries and the maxillaries, or, 
more frequently by the praemaxillaries only. Parietal bones 
united in a sagittal suture, or separated by a fontanelle; oper- 
cular bones well developed; symplectic present. Lower pharyn- 
geal bones falciform, subparallel to the branchial arches, pro- 
vided with teeth arranged in one, two, or three series, and often 
remarkably specialised. Ribs mostly sessile; no parapophyses in 
the thoracic region; epipleurals and epineurals, mostly free, 
floating. Pectoral fins inserted very low down, folding hke the 
ventrals. Body naked or scaly. No adipose dorsal fin. 
The brain-case is produced forward to the nasal capsule. 
The branchiostegal rays are reduced to 3; the branchiostegal 
membrane is usually more or less extensively grown to the 
isthmus. The sulorbital branch of the sensory canals is usually 
produced on the operculum, as in the Characinidae. The ventral 
rays number 7 to 12, rarely 5 or 6. Pyloric appendages to the 
stomach are absent. 
Freshwater fishes feeding on vegetable substances or small 
animals, and dispersed over the whole world with the exception 
of South America, Madagascar, Papuasia, and Australasia. The 
species are exceedingly numerous, about 1500 being known, 
referable to four sub-families, as proposed by Sagemehl. 
(1.) CATOSTOMINAE.— Margin of upper jaw formed in the middle 
by the small praemaxillaries and on the sides by the maxillaries, 
which are hidden in thick fleshy lips; no barbels; pharyngeal 
teeth in a single row, very numerous, comb-like; air-bladder 
large, divided into two or three parts by transverse constrictions, 
not surrounded by a bony capsule. Mostly from North America ; 
two species from China and one from Eastern Siberia. Fossil 
in the Lower Tertiary of North America. 
Principal genera:—Sclerognathus, Carpiodes, Catostomus, Moxo- 
stoma. 
1 For the anatomy and physiology, ef. C. Sachs’s posthumous work, Untersuch- 
ungen am Zitteraal, edited by E. du Bois-Reymond (Leipzig, 1881). 
