1002 



CLASS PISCES. 



Eocene of Barton, we have Siluroids referred to the existing tropical 

 genus Arius ; the peculiar, somewhat heart-shaped, otoliths of these 

 fishes being not uncommon in the Barton beds. It is interesting 

 to notice the association in the English Eocene of Siluroids with 

 Crocodiles and Trionychoid Chelonians ; the three groups being 

 found together at the present day in India and Africa. The Eocene 

 of Sumatra has yielded remains of extinct species of the living 

 Oriental genera Pseudotropius and Bagarius ; the last-named genus 

 being also represented in the Pliocene Siwaliks of India by the 

 gigantic B. Yarrelli, now inhabiting the 

 Ganges. The same beds have also yielded 

 remains of C/arias, now found in both the 

 Oriental and Ethiopian regions, of a species 

 belonging to the genus Heterobranchus (fig. 

 938), which is now confined to the Nile, 

 and not improbably also of Chrysichthys of 

 tropical Africa. The existing Macrones 

 aor of the Indian and Burmese rivers has 

 also left its remains in the Siwaliks ; while 

 the characteristic Oriental genus Rita is 

 likewise represented in the same deposits. 

 Finally, of the widely-distributed genus 

 Arius, which we have already mentioned 

 from the English Eocene, there is evidence 

 of two Siwalik species ; one being appa- 

 rently nearly allied to a large existing West 

 African form. In the Eocene of North 

 America there occurs the genus Rhineastes, 

 which has vomerine teeth, and may be 

 allied either to Arius or to Pimelodus, 

 while spines from the same deposits have been referred to the 

 latter genus. 



Family Murjenid^. — The last family that we have to notice in 

 this suborder is that of the Eels. In these fishes the body is greatly 

 elongated, and either naked, or covered with rudimental scales ; the 

 toothed maxillae form part of the border of the upper jaw, and 

 there are no pelvic fins. Of the freshwater forms, Anguilla (Eel) 

 ranges from the present date to the Chalk of the Lebanon, and is 

 abundantly represented in the Miocene of CEningen and the Middle 

 Eocene of Monte Bolca. The Marine forms, or Congers, are repre- 

 sented by species of the existing genus Ophichthys in the Monte 

 Bolca beds; and by the extinct Sphagebranchus of the latter deposits, 

 and Rhynchorhinus of the London Clay. Peculiar larval forms of 

 the type known as Leptocephali occur in the Continental Tertiaries, 

 some of which are probably referable to this family. 



Fig. 938. — Upper view of the 

 skull of Heterobranchus inter- 

 medins; from the Nile. One- 

 half natural size, a, Supraocci- 

 pital, and b, Frontal vacuities ; 

 eth, Ethmoid ; fr, Frontal ; or, 

 Orbit ; sup, Supraoccipital ; tu, 

 Turbinal. The sculpture is 

 omitted. 



