Classijicaiion of the Order Ostariophysi. 575 



small, feAv-rayed ; anal short or long ; pelvics 6-rayecl, below 

 the dorsal. Head depressed ; nostrils remote, without 

 barbel; villiforra teeth in the jaws; palate toothless. 

 Palatine rod like ; mesopterygoid, when present, small, 

 attached to lateral ethmoid ; operculum reduced, scarcely 

 larger than a branchiostegal ray, but attached anteriorly to 

 the iuteroperculum. Skull depressed, the pterotics with 

 strong lateral laminar projections. No post- temporal ; 

 supra-cleithrum forked^ the lower limb slender, running to 

 basioccipital, the upper extending neaiiy to the middle of 

 the supradccipitfil ; no mesocoracoid ; hypocoracoids inter- 

 locking below. Vertebrae 34 to 75 (10 + 24-65), strongly 

 compressed, with laminar neural and hsemal spines and 

 M'ith a series of horizontal lateral processes arising on each 

 side from the middle of the centra ; free praecaudal vertebrae 

 without parapophyses, with sessile ribs ; fifth vertebra rather 

 long, rigidly united with complex, their neural spines 

 forming a low ridge of bone with thickened dorsal edge 

 wiiich joins the supraoccipital anteriorly; parapophysis of 

 fifth vertebra a very strong process ; parapophysis of fourth 

 a lamina, united posteriorly to the base of the fifth, anteriorly 

 decurved and united to the stem of the supra-cleithrum. 

 Air-bladder large, free, partly constricted into two lateral 

 portions. 



South -American fresh-water fishes. 



Biinocephalus , Bunocephalichthys and Dysichthys liave a 

 short tail, anal 5- to 9 rayed, and about 24- caudal vertebra?. 

 Platystacus (Aspredo) has a long tail, anal 50- to 60-rayed, 

 and 60 or more caudal vertebrae. 



Family 22. Callichthyidse. '^' 



Body armoured with two series of overlapping bony 

 laminae on each side. Gill-membranes broadly united to 

 isthmus. Dorsal fin anterior ; adipose tin with a spine ; 

 anal short; pelvics below the dorsal. Mouth small, ter- 

 minal ; praemaxillaries small, movably attached to meseth- 

 moid ; rami of lower jaw slender; jaws with or without 

 feeble teeth ; palate toothless ; one or two pairs of maxillary 

 barl)els. Palatine articulating with anterior end of lateral 

 ethmoid; pterygoid and mesopterygoid absent; anterior 

 end of metapterygoid connected with lateral ethmoid and 

 palatine by a ligament. Bones of cranial roof more or 

 less expanded and plate-like; suborbitals well-ossified, with 

 an inner shelf; operculum large. Post-temporal absent; 

 supra-cleithrum a large plate ankylosed with the pterotic, 

 connected with sphenotic and supra-occipital above, prootic 



