ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 405 



disagrees with Baur regarding the types of some of the genera of that 

 author, and particularly on the value of some of these genera. 



Phylogeny of the Teleostomi.* — C. T. Began gives the following 

 classification of the Teleostomi, the relations of the different orders 

 being indicated thus : — • 



Teleostei 



Dipneusti Placodermi 



Crossopterygii 



Chondrostei 



The Chondrostei and Crossopterygii correspond to the groups usually 

 so named ; the Dipneusti comprise the Sirenoidei only ; the Placodermi 

 include the Arthrodira, Antiarcha, and Osteostraci ; and to the Teleostei 

 the Ganoidei Holostei are added. 



Oral Breathing-Valves of Teleostei.f — E. G. Mitchell has studied 

 these in a large number of species. They are sheets of membrane com- 

 posed of elastic connective tissue, covered with a mucous membrane con- 

 tinuous with that lining the mouth. They are situated in the mouth- 

 cavity behind the maxillary and mandibular teeth, and their function is 

 to prevent regurgitation of the water through the mouth in the act of 

 breathing. Their size and shape are dependent on the size and shape of 

 the mouth. In fishes with inferior mouths the upper valve is well 

 developed, while the lower is reduced or absent ; terminal-mouthed fishes 

 have upper and lower valves nearly equal, while in upwardly directed 

 mouths, e.g. Echeneis naucrates, the maxillary valve is the smaller. 



Gill-Arches of Muraenidae.J — Canna M. L. Poppa gives a careful 

 account of the structural characters of the branchial arches in Anguilla, 

 Conger, Ophicthys, Murama, and other eel-fishes, and shows that the 

 peculiarities are specifically diagnostic. This is of value, but, as the 

 author points out, the study is incomplete without an interpretation of 

 the structural peculiarities in reference to the peculiarities in mode of 

 life, especially as regards diet. 



Fresh-water Fishes of Mexico.§ — S. E. Meek notes that in Mexico 

 there are four quite distinct fish faunas, and though they overlap at the 

 borders, the region of each may be fairly indicated on the map. The 

 origin of the fish is given, approximately, as from the Colorado river, 

 from the Rio Grande, from the Lerma, and from Central America. The 

 paper contains interesting notes on viviparity, which seems to be the 

 rule amongst the tropical Pceciliidre. It appears that in the tropical 



* Ann. Nat. Hist., Ixxvii. (1904) pp. 329-49. 



t Amor. Naturalist, xxxviii. (1904) pp. 153-G4. 



J Ann. Sci. Nat., xix. (1904) pp. 367-90 (20 figs.). 3 



§ Amer. Naturalist, xxxvii. (1903) pp. 771-84. 



