60 PERCESOCES. 
the diameter of which is 33 to 4 in the length of head; interorbital width 3 to 34 in the length of head 
Teeth small ; lower jaw slightly projecting; maxillary slightly exposed distally, not quite reaching the 
vertical from the anterior margin of eye. 15 or 16 gill-rakers on the lower part of the anterior arch. 
Scales with crenate edges, (38) 40 to 45 in a longitudinal series. Dorsal III-V, I 9-11; origin of 
spinous dorsal usually nearer to base of caudal than to tip of snout; last dorsal spine inserted a little 
in advance of the origin of anal, which is below the membrane connecting the spine to the back. 
Anal I 17-20 (21). Pectoral ? to 4 the length of head, extending a little beyond the base of ventrals. 
Caudal forked. Caudal peduncle 2 to 24 as long as deep. 
Hab. Mexico, Rio Lerma System and the Valley of Mexico: 
Lake Chapala?; Lake Cuitzeo!; Xochimilco. 
Here described from four specimens from Xochimilco (Week), measuring up to 
100 mm. in total length. | 
6. Chirostoma humboldtianum. 
Atherina humboldtiana, Cuv. & Val. Hist. Nat. Poiss. x. p. 479, t. 306 (1835) *. 
Atherina vomerina, Cuv. & Val. t. c. p. 481°. 
Atherinichthys humboldtii, Giinth. Cat. Fish. iii. p. 404 (1861) *. 
Chirostoma humboldtianum, Steind. Denkschr. Ak. Wien, Ixii. 1895, p. 522, t. 1. fig. 1/4; 
Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1896, p. 793°; Jord. & Snyd. Bull. U.S. Fish. 
Comm. xix. 1899, p. 184°; Meek, Publ. Columbian Mus., Zool. v. 1904, p. 175’. 
Depth of body 4 to 53 in the length, length of head 33 to 4. Snout from as long to twice as long as the eye, 
the diameter of which is 3 to 53 in the length of head; interorbital width 33 to 33 in the length of 
head. Teeth rather small; jaws equal anteriorly or the lower a little projecting ; lower jaw less than 
2 the length of head; maxillary exposed distally, extending nearly to the vertical from the anterior 
margin of eye. 16 to 19 gill-rakers on the lower part of the anterior arch. Scales with edges usually 
crenate ; 48 to 62 in a longitudinal series. Dorsal IV-VI, I 10-13; spinous dorsal in advance of anal, 
its origin usually a little nearer to base of caudal than to tip of snout. Anal 117-20. Pectoral 2 to 4 
the length of head, extending to above anterior part or middle of ventrals. Caudal forked. Caudal 
peduncle 2 to 2% as long as deep. 
Hab. Mexico, Rio Lerma System and the Valley of Mexico: 
Lake Juanacatlan ‘ (Buller); Lake Ayotla (Buller); Lake Patzcuaro’; City of 
Mexico! (Doorman); Texcoco*; Lake Chalco®? (Jordan); Xochimilco? (Meek, 
Gadow). 
Here described from a large series of specimens, measuring up to 240 mm. in 
total length. Dr. P. Pappenheim has very kindly examined the type of the species 
on my behalf and has sent me a photograph of it, which leaves no doubt that the 
species above described is the true C. humboldtianum. 
7. Chirostoma estor. 
Chirostoma estor, Jord. Proc. U.S. Nat. Mus. 1879, p. 2987; Steind. Denkschr. Ak. Wien, Ixii. 
1895, p. 523, t. 1. fig. 2° ; Meek, Publ. Columbian Mus., Zool. v. 1904, p. 180°. 
Lethostole estor, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 1896, p. 792 *. 
Depth of body about 5 in the length, length of head 33 to 4. Snout 14 to 2 as long as eye, the diameter of 
which is 4 to 53 in the length of head; interorbital width 4 in the length of head. Teeth small; 
