SOUTH AMERICAN NEMATOGNATHI. 167 



behind the ventrals to behind the anal fin; body and fins 

 everywhere covered with minute black points. 

 Head 3J; depth 2|; D. I, 7-8; A. 7-8; Lat. I. f^ 



LOEICARIID^. 



I. Plecostomus* Gronowius. 

 Hi/postomus Lac^pede; Cochliodon Heckel. 



§ Cochliodon. 



1. Plecostomus cochliodon (Kuer.) 



Cochliodon Iiyposiomns Heckel MS. 



§ Plecostomus. 



2. Plecostomus spinosissimus Steindacbner. 



3. Plecostomus emarginatus Cuv. & Val. 



H. horr'idua Kuer; PI. scapularius Cope; PI. tenuicauda Steindacbner. 

 Localities: Cudajas; Santarem; Mauacapuru; Touautius; Obidos; 

 Fonteboa; Tabatinga; Hyavary; Sao Paolo; Goyaz. 



4. Plecostomus limosus sp. uov. 



Types, No. 7869. Four specimens .25 m. Rio Grande do Sul, from 

 tbe Emperor's collection. 



*Tbe species of tbis genus are all closely allied, and tbe new species can 

 best be described by tbe following key, wbicb represents tbe relationsbips, as 

 near as we can trace tbem : 



a. D. I, 7. 

 b. A. 5. 



c. Jaws witb 7 or 8 broad tipped teetb (Cocbliodon). cochliodon 1 

 cc. Jaws witb numerous fine teetb (Plecostomus). 



d. Head witb tbree distinct ridges, snout pointed, bead usually 

 elevated, occipital bone ending in a pointed occipital process, 

 e. Ventral surface covered witb small plates. 

 /. Free margins of tbe lateral plates witb long spines. 



spinosissimus 2 



f. Free margins of tbe lateral plates witb sbort spines or none. 



g. Post-bumeral ridge becoming strongest on tbe tail, wbicb 



is flat below. emarginatus 3 



gg. Post-bumeral ridge strongest in front, lower surface 



of tail similar to tbe upper surface. 



2d See. Vol. I. (12) Issued July 18, 1888. 



