4 o 4 



PATAGONIAN EXPEDITIONS : ZOOLOGY. 



r/tosHS Gronow; Hypostomus robinii 

 Gill; Plecostomus brasiliensis Bleek- 

 er; Plecostomus semiitudus Eigen- 

 mann & Eigenmann; Plecostomus 

 boulengeri Eigenmann & Kennedy. 

 Habitat: La Plata north to Trinidad; 



not in southeastern Brazil. 

 2. Plecostomus commersonii (Cuvier & Va- 

 lenciennes), Regan, 206. 



relationships, and for the purpose of discussing the geo- 

 graphical distribution, it will be better to recognize a 

 larger number of genera. My estimate of the character 

 of these can best be expressed by the following key, in 

 which I have followed to a very large extent the 

 phraseology of Regan, but in which are recognized 

 a larger number of genera than are admitted by him. 

 The list of species is accepted with but slight modifica- 

 tions from Regan. 



SUBFAMILIES OF LORICARIID^E. 



a. Haemal spines all simple ; lower and fourth upper 

 pharyngeals not toothed ; anterior rudimentary ray 

 of ventral normally shaped, but internal and 

 directed forwards, upper part of the body pro- 

 tected by bony scutes. 



b. Lower transverse portion of clavicles and cora- 



coids not exposed; margin of snout naked or 

 covered with small granular plates. 



PLECOSTOMIN/E. 



bb. Lower transverse portion of clavicles and cora- 



coids exposed ; margin of snout composed of 



more or less firm plates. HYPOPTOPOMATIN.*. 



CM. Haemal spines of the vertebrae above the anal fin 



bifid ; lower and fourth upper pharyngeals 



toothed. 



c. No anterior rudimentary ray of ventral ; caudal 



peduncle elongate and strongly depressed ; 

 upper part of body with bony scutes. 



LORICARIIN^:. 



cc. Anterior rudimentary ray of ventral internal, 

 plate-like; caudal peduncle cylindrical or 

 compressed. 



d. Upper part of body with bony scutes; abdo- 

 men with a large, regular, nearly square 

 patch of small granular plates, naked at the 

 sides and anteriorly and posteriorly. 



NEOPLECOSTOMIN^. 

 PLECOSTOMIN.*. 



a. First scute of lower lateral series posterior to the 

 temporal plate, with which the second is not in 

 contact. 



*. Premaxillaries nearly equal in length to the den- 

 taries, and with about the same number of 

 teeth. 



Plecostomus spiniger Hensel ; Pleco- 

 stomus limosus Eigenmann & Eigen- 

 mann; f Plecostomus aspilogaster, 

 Cope. 



Habitat: La Plata Basin, including Rio 



Grande do Sul; eastern Brazil. 

 3. Plecostomus punctatus (Cuvier & Valen- 

 ciennes) , Regan, 207. 



Hypostomus subcarinatus Castelnau ; 



c. Operculum and interoperculum little, and not 



independently movable. 

 d. Snout granular to its margin. 

 e. Adipose fin present. 



/. Operculum and interoperculum not 



margined with bristles. 

 g. Body covered with plates. 



I. Plecostomus Gronow. 

 gg. Body naked. 



2. Lithogenes Eigenmann. 

 ff. Operculum and interoperculum with 

 well-developed marginal bristles. 

 3. Pogonopoma Regan. (Type, 

 Plecostomus wertheimeri Steind.) 

 ee. Adipose fin absent. 



h. Operculum and interoperculum with 

 well-developed marginal bristles. 

 4. Canthopomus Eigenmann nov. 

 hh. Operculum and interoperculum not 

 margined with bristles. 



5. Rhinelepis Spix. 



hhh. Adipose replaced by a low median 

 crest. No externally visible oc- 

 cipital crest. 



6. Corymbophanes Eigenmann. 

 dd. Snout with a naked margin. 



7. Hemipsilichthys Eigenmann & Eigenmann. 

 cc. Interoperculum more or less freely movable, 



usually spinate or bristly. 



i. Snout granular to its margin. 



/. Teeth numerous, bifid. 



k. Interoperculum usually armed with 

 slender spines with hooked apices 

 which can be everted and com- 

 pletely retracted beneath the oper- 

 culum. 



/. Sides of head without bristles. 

 m. Last dorsal ray connected with 

 the scute by an inconspicu- 

 ous membrane at its base. 

 n. Dorsal with I, 7 or I, 8 



rays. 



8. Hemiancistrus Bleeker. 

 nn. Dorsal with I, 10 or 



I, 13 rays. 



9. Pterygoplichthys Gill. 

 mm. Last dorsal ray attached by 



