58 



ATHERINID^ : SILVERSIDES 



In a series of vagrans from Galveston, Texas, Jordan and Gilbert 

 counted 14 to 17 soft anal rays. These figures indicate that vagrans 

 and LACINIATUS intergrade, and should be regarded as subspecies. 



XXIV. THYRINA Jordan and Culver, 1895. 



Thyrina Jordan and Culver, Proc. Cal. Acad. Set., (2), 5, 418, 1895; Jordan and 



Evermann, Bull. U. S. Nat. Mus., 47, pt. 1, 803, 1896; Regan, Biol. Centr.- 



Amer., Pisces, 63, 1907. 

 Orthotype. — Thyrina evermanni Jordan and Culver. 

 Melaniris Meek, Publ. Field Mus. (ZooL), 3, 117, 1902. 



Orthotype. — Melaniris balsanus Meek. 

 Range. — Coastwise districts from western Mexico (exclusive of the Rio Lerma 



system) and Central America, south to Colombia and Rio de Janeiro, 



Brazil; chiefly in fresh water. 



Thyrina is very close to Menidia, which it represents in the regi- 

 ons named above. It differs from Menidia, as described in this paper, 

 in several respects. Trunk region shortened, and sharply compressed 

 ventrally, subcimeate in cross section ; air-bladder extended backward 

 into the urosome, as a widely rounded diverticulum, over the first third 

 of the anal base, and visible through the translucent body wall. Lower 

 jaw included ; premaxillary teeth heterodont, the inner teeth in a narrow 

 band or irregular series ; the outer teeth uniserially arranged, and 

 somewhat enlarged (less enlarged than in Archomenidia, and not 

 directed outward). Anterodorsal contour of body nearly straight, and 

 nearly parallel with the posterodorsal contour, the form of the body 

 resembling that of Gambusia. Pectoral fin falcate, usually longer than 

 head ; first dorsal origin well behind origin of anal fin ; anal base longer 

 than head. Circuli as well as radii obsolescent on exposed field of 

 scales ; scale-margins frequently crenate, particularly on the back. 



It seems almost certain to us that Mr. Regan has unduly reduced 

 the number of species of Thyrina. After having examined all of the 

 described species except guatemalensis, we are disposed to accept all 

 as valid. 



88. Thyrina meeki Miller, 1907.-^'- 



Thyrina meeki Miller, Bull. Amer. Mus. Nat. Hist., 23, 110, fig. 2, 1907; Meek. 

 Publ. Field Mus. (Zool.), 7, 139. 1907. 

 Type-locality. — Rio Motagua. at Gualan, Guatemala. 

 Range. — Motagua River and tributaries, on the Atlantic slope of Guatemala. 



