1917.] NATURAL SCIENCES OF PHILADELPHIA. 307 



verticals; pectorals falcate and elongate, reaching nearly to or even 

 beyond, the tips of the pelvic fins. 



Two specimens of T. pachylepis are at hand; they were collected 

 January 5, 1908, by Anastasio Alfaro, in the Estero at Tivives near 

 Puntarenas in Costa Rica. Lengths to base of caudal, 88 and 113 

 mm. The so-called annuli or seasonal rings on the scales are well 

 developed, and resemble those of California Atherinids; the scales 

 .show respectively 2 and 3 of these rings, probably indicating the 

 age in years of the two fishes. Dorsal rays, IV-I, 7 (both specimens) ; 

 anal, I, 20 and I, 21; pectorals reaching a little past tips of pelvics, 

 their length being contained 3.4 and 3.6 times in the total. Scales 

 40-9 and 42-9. 



AUSTROMENIDIA new genus. 



Athcnnichlhys (in part) Giinther, Cat. 3, p. 402 (not Atherinichthys Bleeker = 



Ckirostoma Swainson). 

 Basilichthys of authors (not of Girard, Proc. Acad. Nat. Sci. Phila,, 1854, 



p. 198, microlepidotus = regia, hence Basilichthys = Gastroplerns Cope = 



Pisciregia Abbott; see Thompson, Proc. U. S. Nat. Mus., 50, 1916, 



pp. 4G3-466). 



Genotype. — Basilichthys regillus Abbott. 



Austromenidia is used to replace Basilichthys of authors and not of 

 Girard, whose original type belongs to the genus later called Gas- 

 tropterus and Pisciregia. 



The fishes of this genus, referable to several species, inhabit both 

 coasts of southern South America. They are of comparatively 

 large size, and are of commercial importance. The scales are notably 

 small, numbering from 67 to over 100 in lateral series. Both jaws 

 are strong and arched downward posteriorly; the premaxillary is 

 dilated distally. The teeth are disposed in narrow l^ands along the 

 jaws, and are usually absent from the vomer, although a few teeth 

 or even a small patch, may be present on that bone. The first dorsal 

 fin begins well before the anal, at a point about midway between base 

 of snout and base of caudal. 



It will be noted from the foregoing diagnosis that Austromenidia 

 resembles Menidia very closely, differing from it in the larger size, 

 the stronger jaws, and the much finer scales. 



The species of Chirostoma, confined to the fauna of the Lerma 

 River System in Mexico, form a large series with diverse extremes. 

 The scales are usually larger (37 to 75)^ than in Austromenidia; the 



2 Regan's extreme count for diazi; the number probably includes the scales 

 on the base of the caudal fin.. The scales are usually larger in Chirostoma. 



