576 On the Classification of the Order Ostariophysi. 



and cxoccipital below, and parapophysis of fourth vertebra 

 behind ; clei thrum transversely expanded ; mesocoracoid 

 present; hypocoracoids interlocliing below. Vertebras 

 27-32 (13-18 + 12-14) ; caudal vertebrae normal, with 

 slender neural and haemal spines ; prfecaudal vertebise, from 

 seventh to last, with slender ribs, all {Corydoras) or the 

 anterior sessile ; sixth vertebra free, with a strono; rib sup- 

 porting the first lateral plate of the lower series, borne on a 

 stout parapophysis which articulates with that of the fifth 

 vertebra ; complex vertebra ankylosed with fifth and with 

 skull, its parapophyses forming with the supra-cleithra and 

 exoccipitals apair of subcylindrical capsules opening laterally 

 beneath clefts in the supra-cleithral plates ; air-bladder 

 divided into two sacs enclosed in the capsules. 



South-American fresh-water fishes. 



Genera : Scleromystox, Callichthys, Hoplusterniim, Deca- 

 pogon, Dianema, Corydoras. 



Family 23. Loricariid?e. (Fig. 2, A.) ^-^ 

 Body naked, or armoured with bony scutes, which ante- 

 riorly form five longitudinal series on each side. Gill- 

 membranes broadly united to isthmus. Dorsal fin anterior; 

 anal short; pelvics below or in advance of the dorsal. 

 Mouth inferior, with expanded lips forming a sucker ; prse- 

 maxillaries movably articulated with mesethmoid ; jaws 

 toothed ; palate toothless ; a pair of maxillary barbels. 

 Palatine articulating Avith anterior end of lateral ethmoid ; 

 pterygoid and mesopterygoid absent. Post-temporal absent ; 

 supra-cleithrum a large plate united with pterotic and 

 supra-occipital above, prootic and exoccipital below, and 

 parapophysis of fourth vertebra behind; cleithrum trans- 

 versely expanded ; mesocoracoid present. Vertebrae 27 to 38 

 (10-18 + 14-26); caudal vertebrae compressed, with neural 

 and haemal spines more or less expanded ; free praecaudals 

 without parapophyses, with sessile ribs ; a pair of very 

 strong sessile ribs borne by the sixth vertebra, which is rigidly 

 united to the fifth and articulates with the seventh by a 

 hinge which restricts lateral movement; complex vertebra 

 united to fifth and to skull by suture or ankylosis ; parapo- 

 physes of fifth vertebra absent, of fourth forming with 

 supra-cleithra and exoccipitals a pair of capsules opening 

 laterally beneath the notched or perforted supra-cleithral 

 plates ; air-bladder reduced to two sacs enclosed in the 

 capsules. 



South-American fresh-water fishes. 



