HOPLOPLEURIDiB. 665 



hranchice none; air-Uadder present, divided in the interior. 

 The ova fall into the cavity of the abdomen hefore exclusion. 

 On each side a parieto-mastoid cavity leading into the interior 

 of the skull. 



One genus only {Notopterus) with five species which 

 inhabit fresh waters of the East Indies and West Africa. 

 Well-preserved remains of this genus occur in the marl slates 

 of Padang, in Sumatra. Their air-bladder is divided into 

 several compartments, and terminates in two horns anteriorly 

 and posteriorly, the anterior horns being in direct connection 

 with the auditory organ. 



Twenty-Seventh Family — Halosauridje. 



Body covered with cycloid scales ; head scaly ; iarbels none. 

 Margin of the upper jaw formed hy the intermaxillaries mesially, 

 and by the maxillaries laterally. Opercular apparatus incom- 

 plete. Adipose fin none. The short dorsal belongs to the 

 abdominal part of the vertebral column; anal very long. 

 Stomach with a blind sac ; intestine short ; pyloric appendages 

 in moderate number. Pseudobranchice none. Air-bladder large, 

 simple ; gill-openings wide. Ovaries closed. 



The only genus belonging to this family was discovered 

 by the Madeiran ichthyologist Johnson, in 1863 ; but since 

 then the naturalists of the "Challenger" expedition have 

 added four other species, showing that this type is a deep-sea 

 form and widely distributed ; the specimens were dredged in 

 depths varying from 560 to 2750 fathoms. 



Twenty-Eighth Family — HoplopleueidjE. 



Body generally with four series of suUriangular scutes, and 

 with intermediate scale-like smaller ones. One (?) dorsal only ; 

 head long, with the jaws produced. 



