64 PEKCESOCES. 



1. Thyrina guatemalensis. 



Atherimchthys guatemalensis, Giiuth. Proc. Zool. Soc. 1864, p. 151 \ and Trans. Zool. Soc. vi. 



1869, p. 4J3^ 

 Thijrina evermanni, Jord. & Ciilv. Proc. Calif. Ac. Sci. (2) v. 1895, p. 419 ' ; Jord. & Everm. 



Bull. U.S. Nat. Mus. xlvii. 189G, p. 804 ' ; Meek, Publ. Columbian Mus., Zool. v. 1904, 



p. 184 '. 

 Thijrlna crystaUiiia, Jord. & Culv. t. c. p. 420''; Jord. & Everm. 1. c. ' ; Meek, 1. c. ". 

 Menidia guatemalensis, Jord. & Everm. t. c. p. 801 ". 

 Melaairis balsanus, Meek, t. c. p. 183, fig. 64'". 



Depth of bod}' 4 to 5 in the length, length of head 4| to 4^. Snout shorter than eye, the diameter of which 

 is 2| to 3 in the length of head; intcrorbital width 2^ in the length of head. Teeth in hands, tlie 

 outermost series enlarged ; jaws equal anteriorly ; maxillary not exposed, extending nearly to below 

 the eye. 16 or 17 gill-rakers on the lower part of the anterior arch. Scales with entire edges, 3(i to 42 

 in a longitudinal series. I)orsal IIl-IV, I 7-9 ; origin of spinous dorsal above sixth ray of anal. 

 Anal I 19-2.5, ending below or a little behind the end of the second dorsal. Pectoral falcate, longer 

 than the head, extending heyond the middle of ventrals. Caudal forked, the low^er lobe somewhat the 

 longer. Caudal peduncle Ij to 2 as long as deep. 



Hal. Pacific Coast Eivers and Lakes of Mexico and Central America, perhaps 

 entering the sea : 



Eio Presidio ^ ^ and Rio Balsas i'' in Mexico ; Iluamuclial ^ " in Guatemala. 



Here described from the types of the species from Huamuchal (Salvin), and 

 co-types of T. evermnnni and T. crystallina from the Ptio Presidio and of M. balsanus 

 from the Eio Balsas, seveial specimens measuring up to 85 mm. in total length. 

 Estuarine specimens have the pectoral fins longer and more acute than those from 

 inland localities. T. pacligleijis, from tlie Coast of Panama, is closely allied, but has 

 laciniate scales. Gill and Bransford (Proc. Ac. Philad. 1877, p. 187) record 

 T. guatemalensis from Lake Nicaragua, but this identification must be regarded as 

 probably incorrect. 



3. XENATtlERINA, gen. nov. 

 The very aberrant little Atherine described by Meek under the name of Menidia 

 lisa may be regarded as the type of a genus distinct from Chirostoma, characterized 

 by the mouth extending to below the eye and by the peculiar disposition of the 

 scales. 



1. Xenatherina lisa. 



Menidia lisa, Meek, Publ. Columbian Mus., Zool. v. 1904, p. 182, tig. 63 '. 



Depth of body .5 in the length, length of head 4. Snout shorter tlian eye, the diameter of which is 2\ to 2^; 

 in tho length of head and greater than the intcrorbital width. Teeth small ; mouth oldiquo ; jaws e(]ual 

 anteriorly : maxillary extending to below anterior \ of oye. l.'( gill-rakers on the lower part of the 

 anterior arch. Posterior part of body covered with scales, which are continued forward as a scaly band 

 along the middle of the side ; anterior part ol' body naked, except for a dorsal .strip and a ventral patch 



