202 ME. C. TATE BEGAN ON THE 



Subfamily I. Plecostomin J. 



Vertebrae below the dorsal fin with bifid neural spines ; none of the haemal spines 

 bifid ; pharyngeals not toothed ; teeth in the jaws in a single series ; pseudobranchise 

 present ; upper part of the body protected by bony scutes; caudal peduncle compressed, 

 cylindrical, or slightly depressed, with 5 longitudinal series of scutes on each side 

 for its whole length ; lower transverse part of clavicle and coracoid not exposed ; 

 margin of snout naked or covered with small granular plates ; anterior rudimentary 

 ray of ventral internal and directed forwards. 



Key to the Genera. 



I. First scute of lower lateral series posterior to the temporal plate, with which the second is not 

 in contact. 

 A. Prfemaxillaries nearly equal in length to the dentaries and with about the same number 

 of teeth. 



1. Operculum and interoperculum little, and not independently, movable. 



Snout granular to its margin 1. Plecostomus Gronow. 



Snout with a naked margin 2. Hemipsilichthys~E\gmn. 



2. Interoperculum more or less freely movable, usually spinate or bristly. 



a. Snout granular to its margin. 



Teeth numerous, bifid 3. Ancistrus Kner. 



Teeth few, spoon-shaped 4. Panaque Eigmn. 



b. Snout with a naked margin. 



Mouth wide, the length of mandibular ramus nearly equal to the inter- 

 orbital width; naked margin of snout not very wide, without 



tentacles 5. Chcetostomus Tschudi. 



Mouth moderate or narrow, the length of mandibular ramus considerably 

 less than the interorbital width ; naked margin of snout wide or 



with more or less distinct tentacles 6. Xenocara Rgn. 



B. Prsemaxillaries much shorter than the dentaries and with 



fewer teeth 7. Pseudacanthicus Blkr. 



II. First two scutes of the lower lateral series below the temporal 



plate and in contact with it above 8. Acanthicus Spix. 



1. Plecostomus. 



Plecostomus Gronow, Mus. i. p. 24 (1758), and Zooph. p. 127 (1763) ; Bleek. Ned. Tijd. Dierk. i. 



1863, p. 77 ; Gtinth. Cat. Fish. v. p. 230 (1864) ; Eigenm. & Eigenm. Occ. Pap. Cal. Ac. i. 



1890, p. 396. 

 Hypostumus Lacep. Hist. Nat. Poiss. v. p. 144 (1803) ; Cuv. & Val. Hist. Nat. Poiss. xv. p. 489 



(1840), part. ; Kner, Denkschr. Ak. Wien, vii. 1854, p. 256. 

 Rhinelepis Spix, Gen. et Spec. Pise. Bras. p. 4 (1829) ; Cuv. & Val. Hist. Nat. Poiss. xv. p. 479 



(1840), part.; Gunth. Cat. Fish. v. p. 252 (1864) ; Eigenm. & Eigenm. Occ. Pap. Cal. Ac. i. 



1890, p. 414. 

 Body oblong or elongate ; first scute of lower lateral series posterior to clavicle and 



