596 TELEOSTEI CHAP. XXI 
Fam. 6. Aspredinidae—This family is also closely related 
to the Siluridae. The ribs are sessile as in the Loricariidae, but 
inserted very low down on the centra, which higher up bear 
strong transverse processes. The opercular bone is entirely absent. 
The gill-opening is reduced to a foramen in front of the pectoral 
fin. The head is extremely depressed and the mouth terminal ; 
the tail is very slender; the body is naked. The air-bladder is 
large and free, the intestinal canal short. Four genera from 
South America: <Aspredo, Bunocephalus, Bunocephalichthys, 
Dysichthys. Species 18. Aspredo, of the Guianas, the largest 
form, reaching to about a foot in length, is remarkable for the 
manner in which the female carries her eggs. The skin of the 
lower parts assumes a spongy condition about the breeding 
season, and the eggs, after being deposited, become attached to 
the lower surface of the head, belly, and paired fins, forming a 
single layer ; each egg becomes connected with the skin of the 
mother by a cup-shaped, pedunculate base, supplied with blood- 
vessels and coated with a layer of epithelium, the formation of 
which is still unexplained.’ 
1 Cf. Wyman, Amer. Journ. Sci. (2) xxvii. 1859, p. 9, and Vaillant, C. R. Ac. Sez. 
exxvi. 1898, p. 544. 
