Ixii. PRESIDENT'S ADDRESS. 



side, and undergo remarkable changes. The larvse are per- 

 fectly symmetrical, with an eye on each side of the head, and 

 swim in a vertical position like other fishes. The manner 

 in which one eye is transferred from the lower to the upper 

 side is not accounted for. The head being cartilaginous, 

 it is not difficult to conceive the possibility of its being 

 twisted. They live at the bottom of the sea, and swim with an 

 undulating motion of the body. Rhombus, a genus which in- 

 cludes the Turlot and Brill, has been found fossil in the 

 Miocene Beds of Tuscany and Sicily, and in the Eocene Beds 

 of Monte Bolca. The mouth is furnished with vomerine teeth. 

 Pleuronectes, which includes the Plaice, the Flounder, and the Dal, 

 have none. The Sole, of which there are nearly forty species, 

 inhabits all the suitable localities in the tropical and temperate 

 zones. 



Siluridae, Cat-fish. Of all the Teleostcam this family is more 

 nearly allied to the Ganoidei than any other. The connection 

 is through the Amiidae. Several of this family belong 

 exclusively to the Mesozoic Age. A. calva is its only living 

 representative, it lives in the rivers and lakes of North America. 

 The family Siluridae is represented by numerous genera exhibit- 

 ing a great variety of form and structure of the fins. They 

 inhabit the fresh-waters of all the tropical and temperate regions ; 

 a few enter the sea, but keep near the coast. The first 

 appearance of Siluridse is indicated by fossil remains in some 

 Tertiary deposits of Sumatra. Spines referable to Cat-fishes 

 have been found in the Tertiary formations of North America. 

 The exo-skeleton consists of osseous plates. Cope considers 

 the Sturgeon to be their ancestor. 



Scopelidae, to which Ipnops belongs, is a singular genus 

 discovered for the first time by the Challenger Expedition. 

 Four examples were found off the coast of Brazil at depths 

 varying between 1,600 and 2,150 fathoms, all belonging to the 

 species I. murrayi. The eye seems to have lost its function of 

 ision and assumed that of producing light. Among other 

 Siluridae, the family of Carps is one of the most numerously 



