404 



I'ATAG(^NIAN RXPRDITIONS : ZOOLOGY 



r/tosiis Groncnv; H yl^ostonius robinii 

 Gill; Flccostoiinis brasilicnsis Bleck- 

 er; Plecostovius seviiniidus Eigen- 

 mann & Eigenmann ; Plecostomiis 

 bouleugeri Eigenmann & Kennedy. 

 Habitat : La Plata north to Trinidad ; 

 not in southeastern Brazil. 

 2. Plecostovius coiinnersonii (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 e.vpresscd 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. 



SU UFA MI I.IK 



LORICARIID.I 



Iia;mal 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 e.\posed ; margin of snout naked or 

 covered with small granular plates. 



Plecostomin/E. 



bb. Lower transverse portion of clavicles and cora- 



coids e.xposed ; margin of snout composed of 



more or less firm plates. Hvpdptopom.^tin.t;. 



. Ha;mal spines of the vertebrre 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. 



LOKICARIIN.'E. 



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.k. 



Pi.ECOSTOMIN/K. 



of lower lateral series posterior to the 

 plate, with which the second is not in 



First scul 

 tempor 

 contact. 

 b. Premaxillaries nearly equal in length to the den- 

 taries, and with .ibout the same number of 

 teeth. 



Plccostoiiius .<pinigcr lluiisel; Pleco- 

 stomiis liiiiosus Eigenmann & Eigen- 

 mann ; ? Plecostovius aspilogaster, 

 Cope. 



Habitat: La Plata Basin, including Rio 

 Grande do Sul; uastern Brazil. 

 3. Plecostovius puiietcitiis (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. Plccostomus Gronow. 

 gg. Body naked. 



2. Lithogenes Eigenmann. 



ff. Operculum and interoperculum with 



well-developed marginal bristles. 



3. Pogonopoma Regan. (Type, 



Plccostomus wertheimeri Steind.) 



cc. Adipose fin absent. 



/(. 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. Hemipsilichihys Eigenmann & Eigenmann. 

 cc. Interoperculum more or less freely movable, 

 usually spinate or bristly. 

 I. Snout granular to its margin. 

 y. 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. 

 ». Dorsal with I, 7 or I, 8 

 rays. 

 8. Hemianchlrus Bleeker. 

 ««. Dorsal with I, 10 or 

 I, 13 rays. 

 9. Pterygoplichthys Gill. 

 wiw. Last dorsal ray attached by 



