19S [NOTEMBER; 



of the eye. A few minute spines upon the angle of preopercle. Scales large? 

 conspicuously ciliated posteriorly. Ground color light reddish or reddish brown, 

 maculated with black. 



Inhabits the hydrographic basin of the Rio de Maypo, Chili. 



ATHERTNIDiE. 



This family heretofore composed of the single genus Atherina, having been 

 made on our part the subject of much research, is now understood by us in the 

 following manner. The 



Genus ATHERINOPSIS, Girard, 



Which we have recently established, is to receive such species as have no 

 palatine teeth, with both jaws equal, and the snout more or less rounded. 



Atherina menidia, Linn., and A. notata, Mitch., will come under this denom- 

 ination, alongside with A* calif omiensis, Girard. The 



Genus BASILICHTHYS, Girard, 



is characterised by the protrusion of the upper jaw beyond the lower; adding 

 to that feature small teeth on both jaws, none on either the vomer or palatines, 

 the intermaxitlaries constituting the upper arcade of the mouth, with the maxil- 

 laries placed behind them, and the upper surface of the head scaly ; including : 



4. Basilichthys microlepidotus, G. Atherina microlepidota, Jen. Zool. of 

 Beagle, iv. Fish. 1842, 78. PI. xvi. fig. 1, 1 a. 1 b. Guich. in Gay, Hist, de 

 Chile, Zool. II. 1848,253. 



Inhabits the fresh waters of Chili. 



And also Atherina laticlavia, Cuv. & Val. ; A. argentinensis, Cuv. & Val. j 

 A. macrophthalma, Agass. ; A. bonariensis, Cuv. & Val. and A. lichtensteinii, 

 Cuv. & Val. Finally the 



Genus HETEROGNATHUS, Girard, 



Is based upon the elongation of the lower jaw which projects considerably 

 beyond tbe upper one. There are either no teeth on the palate or else they exist 

 in a very rudimentary state only. 



Atherina humboldtiana, Cuv. & Vax.., and A. vomerina, Cuv. & Val., will, 

 for the present, constitute this genus. 



SILURID^E, 



Genus NEMATOGENYS, Girard. 



Head very much depressed and large. Body posteriorly compressed ; posterior 

 margin of caudal fin rounded. Anal opposite space between the dorsal and 

 caudal. Ventrals under the dorsal. Mouth broad but not deeply cleft; its angle 

 provided with a long barbel. A second pair of subhyoidal barbels shorter than 

 the buccal ones. A still shorter and prenasal barbel constituting a third pair of 

 these appendages. Intermaxillaries and dentaries provided with a patch of 

 card-like teeth. Pharyngobranchials covered with similar asperities. Eyes 

 rather small, situated on the upper surface of head. Opercular apparatus spine- 

 less. Branchial apertures continuous under the throat. A spine at the external 

 margin of the pectoral fins. Skin scaleless. 



5. Nematogenys inermis, G. Trichomycterus inermis, Gnicu. in Gay, Hist, 

 de Chile, Zool. II. 1848, 312, Ictiol. Lam. ix. fig. 2. 

 Inhabits the fresh waters of Chili. 



Genus TRICHOMYCTERUS, (Humb.) Valenc. 



Head depressed and rather small. Body anteriorly rounded ; posteriorly com- 

 pressed. Caudal fin emarginated or subemarginated. Anal under the posterior 

 part of the dorsal, and ventrals in advance of the latter. Mouth small or of 

 medium size, inferior, and provided with a double pair of barbels at its angle* 



