108 General Notes. 
sions in the corresponding arc, and the mean sea level rises with 
the mean eccentricity in the middle of the cycles, and falls at the 
limit between them, and hand in hand with the mean sea level, rises 
and falls also, the temperature in the higher latitudes. 
The doctrine here discussed agrees with Lyell's great principle. 
Slow changes in the length of the winter and summer and in the 
force of the tidal-wave, produce periodical changes of climate, and 
displacements of the beach-lines. The earth changes its form 
slowly and imperceptibly. The changes take place so slowly that 
the effects, first after expiration of many thousands of years,begin to 
appear distinctly. There are two astronomical periods which are 
the causes of the great and radical changes, of which geology leaves 
to us testimonies from remote ages, and which will still continue 
in the future, for millions of years to produce similar changes in the 
geography of the globe, its climate and its animal and vegetable 
life.— ^. Blytt in Christinia Videnkabs Selskabs Forhandlingar, i88g, 
The Western Sahara.— According to the data brought together 
by Sr. C. G. Toni, in the L' Esplorazione Commerciale, from the ex- 
plorations of Spanish and German travelers, the western coast of 
Africa consists of a Cretaceous mass which is continued from the Cre- 
taceous nucleus of Morocco and terminates a^ Cape Blanco,-In imme- 
diate contact with the Cretaceous band of the coast and immediately 
above it, exists a thick deposit of desert sands, which covers all the 
subjacent formations. Beneath this sand through a large portion of 
its extent, rocks of the Devonian period are believed to extend and 
crop out in a few points. The hills of the oasis of Adrar Temar 
contain trachyte and have some peaks of granite and basalt. These 
hills also contain quartz, marble and various siliceous and ferrigen- 
In the " Neues Jahrbuch fur Mineralogie, Geologie und Pale- 
ontologie, Jahrgang, 1888, I Band; drittes Heft," Dr. Ferd. Roemer 
describes and figures a new genus of Echinodermata from Texas, to 
which he gives the name of " Macraster," and calls the only species 
Macraster iexanus. This fossil has long been familiar to the writer 
in his stratigraphic investigations in Texas, and it makes a well de- 
fined horizon near the very top of the immense thickness of lower 
marine Cretaceous in Texas, and does not occur, as Dr. Roemer in- 
fers from the specimens which accompanied it to Germany, with the 
Exogyra texana fauna, a statement which has been verified by Mr. 
Geo. Stolly, the collector. This fact is important because of the 
tendency upon the part of European palaeontologists to underestimate 
the value of the stratigraphic differentiation of the Texas Cretaceous. 
—R. T. Hill. 
C/ENOZoic— Teeth of Elephas antiquus found at Rinconada, 
Cantillana and other places in the province of Seville S; ain, to- 
