December 23, 19 15] 



NATURE 



449 



coming back ■yid the United States in 1875 was 

 appointed Strickland Curator of the Bird Room in 

 Cambridge. 



Salvin's removal to Cambridge necessitated his 

 giving up his house in South Kensington, which 

 had served as a museum and library for the 

 Central American collections, then very rapidly 

 accumulating. To replace this centre a house 

 was taken in Tenterden Street, Hanover Square, 

 and for some years this was the home of hard 

 work and much instructive conversation and 

 debate, for after the scientific meetings of the 

 Zoological Society in the neighbouring square 

 the ornithologists frequently repaired hither to 

 exchange views, criticisms, and ideas. 



The area of the New World which is dealt with 

 in this series of monographs " includes the whole 

 of Mexico south of the Rio Grande as far as El 

 Paso, and thence to the Gila river, and following 

 it as far as the Gulf of California." Some of the 

 neighbouring islands the sea-birds of which are 

 common to those in the adjacent mainland are also 

 included. The whole of Central America, compris- 

 ing British Honduras, Guatemala, southern Hon- 

 duras, Nicaragua, Costa Rica, and Panama, come 

 within the area. In shape the area has been com- 

 pared to a cornucopia, narrowing from the 

 northern breadth of 1140 miles to 45 miles at the 

 isthmus of Panama. From a climatic point of 

 view the area is divided into three zones, the 

 Tierra Caliente, the Tierra Templada, and the 

 Tierra Fria, the middle term of which corresponds 

 roughly with an elevation of 3000 to 5000 feet. 

 But these limits vary on the Pacific and the 

 Atlantic coasts, the greater rainfall on the latter 

 producing a much more luxuriant vegetation than 

 is found on the western slopes. Although the 

 present connection between the North and South 

 American continents is by way of the Central 

 American isthmus, the same does not apply to 

 the tectonic connection. Geologically, the true 

 union of North and South America is through the 

 Antilles, these islands being the peaks of a moun- 

 tain range which forms the true link between the 

 coast ranges of North America and the Andean 

 chain of South America, although even this cannot 

 be said to be a direct continuation of either of 

 them. The isthmus, as a connecting link, is of 

 later date, due to various complex phases of earth- 

 movement, so that the Caribbean Sea, although 

 now forming part of the Atlantic, was in its past 

 history more closely bound up with the Pacific 

 Ocean. 



In the region in question, the formations consist 

 of Tertiary deposits, fossiliferous limestones, sand- 

 stones, and clays, together with igneous rocks and 

 ashes, these being similar to those found in the 

 NO. 2408, VOL. 96] 



coast ranges and in the Andes. Nowhere in the 

 Central American mountains is any pre-Tertiary 

 core exposed, such as is found in many of the 

 mountains of that period elsewhere. The main 

 movements seem to have been completed by the 

 close of the Miocene times, as Pliocene and more 

 recent deposits are only found at comparatively 

 low elevations, and have not been involved in the 

 major movements. The most recent movements 

 have given rise to the coastal plains, which are 

 specially well marked on the Atlantic side of the 

 isthmus. 



Although Godman and Salvin between them 

 covered in their travels but a small part of the 

 extensive area in question, Mr. Godman has given 

 a peculiarly complete and fascinating account' of 

 the physical feature of the "terrain," the fauna 

 and flora of which they investigated, since the 

 former has rightly used the field-notes and records 

 of their numerous collectors and other naturalists 

 who have worked in Mexico and Central America. 



If we exclude the botanical volumes, and Mr. 

 Maudslay's monograph on Archaeology, we shall 

 find the work deals in the main with Vertebrate 

 and Insect forms, and among the vertebrate the 

 birds especially stand out. The total number of 

 species of Mammalia is described as 181, and as 

 Dr. Sclater remarked : 



"^It may fairly be said that (excluding the intro- 

 duced Mures), at least one hundred of the con- 

 stituent species are essentially Neotropical in their 

 character, of have Neotropical affinities, while of 

 the remainder not more than sixty can be said 

 to be decidedly Nearctic. There is, therefore, 

 no doubt that the Central American isthmus, at 

 any rate as far north as Tehuantepec, should be 

 assigned to the Neotropical region." 



More than 1400 species of birds were enumer- 

 ated, of which nearly one-half were endemic. The 

 Reptiles and Batrachia yielded just under 700 

 spec Fes. 



As regards the geographical distribution of these 

 animals. Dr. Giinther remarks that : — 



" A boundary line between the North and South 

 American regions cannot be drawn. Central 

 America forms a transition-tract, unlike any other 

 part of the world, showing the most extraordinary 

 diversity of climatic, physical, and meteoric con- 

 ditions within comparatively small areas, favour- 

 ing the evolution of a great variety of types of 

 genera and species." 



Mr. C. Tate Regan has been responsible for an 

 admirable monograph on the Pisces. He also 

 associates Central America with the Neotropical 

 region. 



Amongst the Invertebrates, besides the insects 



