^770 



SCIENCE. 



[N. S. Vol. V. No. 124. 



from the same area, formed no distinct beach 

 ridges ; at least none have been observed by the 

 writer. In Citrus and neighboring counties the 

 marine Columbia sands seem to be composed of 

 three members — a lower or red member (formed 

 while the shore line was advancing inland), a 

 middle or yellow member (formed mainly dur- 

 ing the culminating period of the subtaergence), 

 and an upper or white member (formed while 

 the shore line was retreating). These rest upon 

 an undulating land surface, rising in a distance of 

 about eight miles, from sda level at Crystal River, 

 to an altitude of about ISO feet A. T., near Le- 

 canto, and again descending to nearly sea level 

 in the Withlacoochee valley. No prominent 

 beach ridges were formed because the shore line 

 did not remain at one level on the slope of the 

 land a sufficient length of time. This is only one 

 of a number of similar cases which might be 

 mentioned where the sea advanced upon and 

 retreated from a sloping land surface without 

 forming beach ridges. 



In regard to the other objections against the 

 lacustrine origin of the Missouri ' upland loess,' 

 presented by Professor Todd, namely, that it is 

 absent from certain areas in the eastern part of 

 the State near the junction of the Mississippi 

 and Missouri rivers and at a low level, I wish 

 to suggest that it may have been there present 

 originally as a very thin sheet which has since 

 almost disappeared because of erosion. Past 

 experience has taught me that when the loamy 

 deposit which constitutes the ' upland loess ' is 

 very thin and patchy and approaches closely in 

 composition and appearance to the residuary 

 clays it is, by many geologists, scarcely recog- 

 nized as a portion of the Loess formation. Tliis 

 suggestion is justified by the fact that I have 

 observed in the region traversed by the St« 

 L. and S. F. railroad, between Cuba and 

 Paciflc City, a loamy clay, usually free from 

 pebbles, apparently separated from the residu- 

 ary clay by a sharp line, and over.spreading the 

 surface of a hilly country like the 'upland loess' 

 in northwestern Illinois. If this is a portion of 

 the Loess formation it indicates that the lake 

 or sea waters rose against the northeastern 

 corner of the Ozark uplift to an altitude of 

 1,000 or more feet, or rather I should say that 

 the land went down to that amount below these 



waters. The superficial silts of this region 

 ought to be investigated. O. H. Hershey. 

 Freeport, III. 



SCIENTIFIC LITERATURE. 

 Birds of the Galapagos Archipelago. By Kobert 

 RiDGWAY. Proc. U. S. National Museum, 

 Vol. XIX., pp. 459-070, 2 pis. Cover title- 

 page dated 1896, but not published till 

 March, 1897. 



It was in the Galapagos Islands that Darwin, 

 during the memorable ' Voyage of the Beagle ' 

 in 1835, made the original observations which 

 led him to discover and formulate the great 

 principle of evolution — to the elucidation of 

 which the remainder of his life was. so success- 

 fully devoted — and it was the birds of these 

 islands which first drew his attention to the de- 

 rivative origin of species. Hence to naturalists, 

 and particularly ornithologists, the Galapagos 

 Islands will ever be classic ground. 



Unhappily, the advent of man, with his reti- 

 nue of goats, pigs, cats and rats, has already 

 resulted in the extermination of at least one of 

 the indigenous birds ; others are threatened 

 with the same fate. The extinction of an ani- 

 mal is always a matter of regret, and in the 

 present case is a serious loss to science because 

 of certain unsolved problems respecting the ex- 

 traordinary and unique interrelations of many 

 of the species. For instance, certain genera 

 contain a large number of forms, alike in color 

 and markings, but differing in proportions, 

 particularly the size and shape of the bill. In 

 one genus {Geospizd) the bill presents a series 

 of types which at first would hardly be sup- 

 posed to fall within the limits of a single family, 

 — much less a single genus. This remarkable 

 series comprises bills that in form and size re- 

 semble those of tanagers, small-billed sparrows 

 and huge-billed grosbeaks. But for the exist- 

 ence of intermediate forms no one would think 

 of placing such diverse kiuds in a single genus. 

 In one or two of the genera almost every con- 

 ceivable stage and step of intergradation exists, 

 so that it becomes extremely difficult — if not 

 in some cases impossible — to draw the line be- 

 tween specific and individual variations. 



Owing to the absence of information concern- 

 ing the adaptations and limits of specific varia- 



