58 PERCESOCES. 



III. Length of head 3 to 3^ in tlie length of tlie fish. Lower jaw projecting, | or a little 

 more than i the length of head. Anal with I 18-24. rays. 20 to 23 gill-rakers on the 

 lower part of the anterior arch. 



A. Teeth small or moderate, close-set ; maxillary exposed distally. 



1. Lower jaw moderately projecting, i the length of head ; pectoral ? to g the length of 



head, extending nearly to above the middle of ventrals. 



50 to GO scales in a longitudinal series . IL hicius. 



60 to 75 scales in a longitudinal series . 12. diazi. 



2. Lower jaw strongly projecting, a little more than i the length of 



head ; pectoral n to | the length of head, extending a little 



beyond the middle of ventrals 13. ocot/ane. 



B. Teeth strong, set rather far apart, in two series; edge of maxillary 



exposed for nearly its wdaole length . 14. sphi/rrena. 



1. Chirostoma bartoni. (Tab. X. fig. 2.) 



Clm-Dstoma hartom, Jord. & Everra. Bull. U.S. Nat. Mus. xlvii. 1896, p. 793'; Meek, PubL 



Columbian Mus., Zool. v. 1904, p. 172'. 

 Chirostoma attenuatum, Meek, 1. c. fig. 55 \ 

 Chirostoma zirahuen, Meek, t. c. p. 174, fig. 57 '. 



Depth of body -3 to 6 in tho length, length of head 4| to 4|. Snout as long as eye, the diameter of whicli 

 is 3i in the length of head and a little less than the interorbital width. Teeth small ; jaws equal 

 anteriorly or the lower very slightly projecting ; maxillary not or but very slightly exposed distall)", not 

 extending to below the eye. 17 or IS gill-rakers on the lower part of anterior arch. Scales mostly 

 with entire edges, 45 to 57 in a longitudinal series. Dorsal IV- V, I 8-10 ; spinous dorsal well in 

 advance of anal, its origin usually nearer to tip of snout than to base of caudal. Anal I 12-15. 

 Pectoral f to 4 the length of head, extending to above base or anterior part of ventrals. Caudal forked. 

 Caudal peduncle 3 to 4 as long as deep. 



Hah. Mexico, "Rio Lerma System : 



Guanajuato^; Lake Patzcuaro ^ ; Lake Zirahuen ■* ; Lerma-. 



Here described from several specimens, measuring up to 100 mm. in total length. 



2. Chirostoma patzcuaro. (Tab. X. fig. 1.) 



Chirostoma patzcuaro, ]\Icck, Publ. Cohunliian Mus., Zool. v, 1904, p, 174, fig. 56 '. 



Depth of body b-\ in the length, length of head 4|. Snout as long as eye, the diameter of which is 35 in the 

 length of head and nearly e(|ual to the iiiterorl)ital width. Teeth small ; lower jaw very slightly 

 prijeoting; maxillary very slightly exposed distally, not extending to below tlie eye, 20 gill-rakei's on 

 llie lower part of the anterior arch. Scales mostly with entire edges, 45 iu a longitudinal series. 

 Dorsal V, I K); spinous dorsal in advance of anal, its origin aliglitly nearer to tip of snout tlian to base 

 of caudal. Anal I 15. I'ectoral ] tlie length of head, extending a little beyond the base of ventrals. 

 Caudal forked. Caudal [ledunclc -i,' as long as deep. 



Hah. Mexico, Rio liCrina System : 

 Ijake Patzcuaro ^ 



Here described from a single specimen from Lake Patzcuaro {Mcel'), measuriu"- 



