PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 241 



9. XiPHiSTER, gen. nov. (Fam. Xii)Msterid(e). 



(Xiphidion Girard, U. S. Pac. R. R. Expl. Fishes. 119; preoccnpicnl in Ortliop- 



tera; Xiphidium, Serv.) 



As the name Xiphidion or Xiplmlium is preoccupied for a geuiis of 



OrMioptera, the name XipMsfer, of siniihxr etymology, is proposed as a 



substitute. The typical species Xipliidion mucosnm, Girard, may be 



knowu as Xipliister mueosus. 



By J. a. €OOFE>«, M. I>. 



Uuiformity in the dates of arrival of birds and laying eggs has usually 

 been considered among the "constants of nature" in the temperate 

 zone. Where the distinction of seasons is well marked, these events 

 are among the most reliable phenomena connected with the climate, and 

 exceptional dates are noted down with particular interest. 



It has, however, been ascertained that there is much less uniformity 

 in the habits of the same species within the tropics. There being no 

 changes of temperature, the division into wet and dry seasons, where 

 existing, can alone influence them. It does so by regulating the How- 

 ering and fruiting of trees, etc., on which the food of birds directly or 

 indirectly depends (except in the case pf aquatic species), the rapacious 

 kinds following the vegetivorons in their search for food. 



Even on the border of the temperate zone, in Arizona "and Florida 

 (probably also in Texas), an approacu to the irregularity of tropical 

 habits has been observed, some species laying-^ eggs in autumn, at the 

 end of the rainy season, and many abandoning the migratory habits 

 seen northward. 



In California we might e:^pectto tind similar conditions, because of the 

 mildness of the winters in the less elevated regions, giving us an almost 

 subtropical climate. But it can only have an efiect south of latitude 

 34°, in the lower part of the Colorado Valley, if anywhere, sufficiently 

 marked to cause the birds to lay in autumn, though its influence is seen 

 to some extent in the wintering of several species farther north than on 

 the east coast. 



As fiir south as frost extends, v.isich is south of San Diego and 

 perhaps to Fort Yuma, the habits of the temperate zone lirevail. At 

 Tucson^ Arizona, however, where Ca])tain Benuire notice<l eggs laid in 

 autumn, the advantage of being about thirty miles south of Fort Yuma 

 is compensated for by the elevation being 748 feet greater. Tiie more 

 barren, almost desert character of the country near Fort Yuma is proba- 

 bly the reason why such habits among the birds are not noticed, perhaps 

 also because no observers have looked for them at the right season. 

 The only peculiar climatic influence observable in California is therefore 

 Proc. Nat. Mus. 79 10 JasE. ^©, 1 abll. 



