20 REPORT OF THE SECRETARY. 



description of the collections of Surgeon Kershner, of the United States 

 Navy, in the Chatham and Auckland Islands, and in New Zealand, and 

 of Mr. I. Russell in the latter place. 



The botany of Kerguelen Island had previously been very thoroughly 

 studied by Dr. J. D. Booker in connection with Sir James Clarke Ross's 

 Antarctic Expedition, (1839-M1.) A number of new phanerogams, ferns, 

 sea-plants, and lichens have been added to the list. 



The zoological collections, though comparatively small, contain an 

 unusual number of new genera and species, especially among the mol- 

 ltisea, insects, Crustacea, echiuoderms, &c, descriptions of which have 

 been furnished to Dr. Kidder by Professors Verrill, S. I. Smith, Dall, 

 Ostensackeu, and Hagen. 



The Bulletin concludes with a study of Chionis minor, a unique and 

 little-known bird, with an attempt to establish its proper position in 

 classification. 



Bulletin No. 4, the catalogue of birds collected by Prof. Francis Su- 

 michrast in Southwestern Mexico, is a scientific account of the collection 

 made in accordance with an arrangement between the Smithsonian In- 

 stitution and Professor Sumicbrast for an extended exploration of the 

 Pacific side of the Isthmus of Tehnantepec for the purpose of procuring 

 specimens of its natural history. During the past four years, four instal- 

 ments of birds have been received and examined by Mr. Lawrence, con- 

 taining 321 species, represented by more than 1,700 specimens, all of a 

 remarkably fine character, and bearing testimony to Professor Suini- 

 chrast's efficiency as an industrious and energetic collector, while the 

 character of the many valuable notes he has contributed manifest his 

 minuteness and intelligence as an observer. 



From this exploration it appears that the region of the Pacific is com- 

 paratively much poorer in birds than that of the Atlantic. This is 

 attributed to the extreme dryness of the soil, to the scarcity of vegeta- 

 tion and of insect life, and to the duration of the winds from the north- 

 east and southwest, which there prevail with great violence. The con- 

 traction of the American continent between the ninety-fourth and 

 ninety-fifth degrees of longitude west from Greenwich, forms what is 

 called, improperly perhaps, the Isthmus of Tehuantepec. In a physical 

 point of view, it may be considered as divided into three parts: first, 

 an eastern, extending from the Gulf of Mexico to the Puerta ; second, a 

 central, from the Puerta to the Chivela; and, third, a western, from the 

 Chivela to the Pacific. The eastern part has its largest portion covered 

 with thick and damp forests, vegetation which rivals the greatest 

 beauties of the tropics. The central region presents an undulating sur- 

 face embossed with innumerable hills which gradually unite on the 

 western side with the mountains of the Sierras. Although watered by 

 numerous streams, it presents but a scanty vegetation, essentially 

 characterized by oaks on one side and palm-trees on the other. The 

 western division, or plains of the Pacific, is very dry, and presents 



