chap. xiv.J THE NEOTEOPICAL REGION. 57 



Buprestidse. — In this family there are no peculiar genera. 

 All the large South American groups are absent, the only im- 

 portant and characteristic genus being Stenogaster. 



Longicorns. — This important group is largely developed, the 

 country being well adapted to them ; and their distribution 

 presents some features of interest. 



In the Prionidse there are 6 peculiar genera, the largest being 

 Holonotus with 3 species ; two others, Derotrachus and Mallaspis, 

 are characteristic ; 3 more are common to South America, and 1 

 to Cuba. The Cerambycidse are much more numerous, and there 

 are 24 peculiar genera, the most important being Sphenothecus, 

 Entomosterna, and Cyphosterna ; while Crioprosopus and Metcdep- 

 tus are characteristic of the sub-region, although extending into 

 South America; about 12 Neotropical genera extend to Mexico 

 or Guatemala, while 12 more stop short, as far as yet known, at 

 Nicaragua. Lamiidse have a very similar distribution ; 13 genera 

 are peculiar, the most important being Monilema, Hamatoderus, 

 and Carneades, while Phcea and Lagochirus are characteristic. 

 About sixteen typical Neotropical genera exXend to Mexico, and 

 15 more only reach Nicaragua, among which are such important 

 genera as Anisopus, Lepturgus, and Callia. 



The land-shells are not sufficiently known to furnish any 

 corresponding results. They are however mostly of South 

 American genera, and have comparatively little affinity for those 

 of the Antilles. 



Relations of the Mexican sub -region to the North and South 

 American Continents. — The sudden appearance of numerous 

 South American forms of Edentata in temperate North America, 

 in Post-Tertiary times, as narrated in Chapter VII., together 

 with such facts as the occurrence of a considerable number 

 of identical species of sea fish on the two sides of the Central 

 American isthmus, render it almost certain that the union of 

 North and South America "is comparatively a recent occur- 

 rance, and that during the Miocene and Pliocene periods, they 

 were separated by a wide arm of the sea. The low country 

 of Nicaragua was probably the part submerged, leaving the 

 highlands of Mexico and Guatemala still united with the North 



