Il6 FlKI.I) COLUMWAX Ml'SKUM ZOOLOGY, V()L. III. 



Gill-rakers 4 + 23 = 27. Length 9.35 inches. Species of large 

 size. La Barca; Ocotlan; La Palma. 



Chirostoma sphyraena Boulenger. 



This is C. diazi Jordan & Snyder. This species was. not taken 

 by us, neither did we get C. cstor from Lago de Chapala, its 

 type locality. 



Chirostoma lermae Jordan & Snyder. 



Of the species of large size of this genus, this one has the 

 strongest dentition. It is known at present only from Lago de 

 Chapala. Gill-rakers 54-20 = 25; base of anal \\ in head, its rays 

 20; length of mandible 2i in head; diameter of eye 5^. Species of 

 large size. The largest in our collection is 9.35 inches in length. 

 Not very abundant. La Palma; Ocotlan. 



Chirostoma o'cotlanae Jordan & Snyder. 



This species is easily recog.nized by its projecting lower jaw, 

 which extends beyond the upper a distance greater than diame- 

 ter of pupil. Teeth minute, in bands; gill-rakers 54-20 = 25; 

 vertebrae 44. Species of large size, longest 10.74 inches. Ocot- 

 lan; La Palma. 



Chirostoma estor Jordan. 



This species was originally described from Lago de Chapala. 

 It was later described by Dr. Steindachner from Lago de Patz- 

 cuaro as C. albus. The identity of C. allnis and C. estor was ques- 

 tioned by Jordan and Evermann from the fact that there were no 

 teeth on the vomer of the specimens in Dr. Steindachner's pos- 

 session. A large number of specimens from Patzcuaro exam- 

 ined by me show that the presence of vomerine teeth is the rule 

 rather than the exception. 



In our collection are specimens from Lago de Patzcuaro, Lago 

 de Zirahuen, and Lago de Xochomilcho. Those from the first 

 mentioned lake are more slender and much lighter and more trans- 

 lucent than those from the other lakes. The general appearance 

 of those from the last two lakes is that of C. humboldtianum^ 

 and at first sight they are easily mistaken for that species. 



Our specimens are from three lakes without outlets; two of the 

 lakes are but 10 miles apart, while the other is considerably remote. 

 Since isolation, this species in each lake has been undergoing 

 some change, but not sufficient to give them rank as species or 



