

Geology and Natural History. 233 



modern than that of the Iowan loess. The list of Florencia fos- 

 sils consists exclusively of species still living in the same region. 

 Every one is doubtless to be found to-day in the flood debris of 

 any creek of moderate size in northwestern Illinois. 



On the other hand, the Iowan loess, as developed at such a 

 typical locality as Iowa City, Iowa, for example, contains an 

 assemblage of species nowhere occurring recent, including some 

 species and varieties now extinct. For comparison with Mr. 

 Hershey's Florencia list of fossils, the following characteristic 

 Iowan loess forms may be mentioned: 



Zonitoides shimeki Pils. Polygyra midtilineata Say. 



Conulus fulvus Drap. Helicina occulta Say. 



Pyramidula strigosa iowensis Succinea avara Say (variety). 



Pils. " lineata W.G.B. " 



Pyramidula striatella Anth. " between lineata and 



Pupa muscorum L. obliqua. 



" blandi Morse. Limnwa humilis Say. 

 jSphyradium simplex G\d. (variety). " desidiosa {?). 



Many others might be enumerated ; but it will be observed 

 that in this brief list of the forms found abundantly at Iowa City, 

 Zonitoides shimeki and the strongly marked variety of Pyra- 

 midula strigosa are extinct ; the Succineas, while probably refer- 

 able to recent species, are still very unlike the living shells ; the 

 Helicina is approaching extinction, being now excessively local 

 and discontinuous in distribution, while several other species do 

 not now occur in the Iowa or Illinois fauna. 



These considerations render it very likely that the Iowan 

 loess fauna is an older one than that of the Florencia formation ; 

 for it is inconceivable that we should have sandwiched between 

 the modern fauna and a prior one in all respects identical with it, 

 a fauna containing extinct species and recognizably differentiated 

 varieties, such as that of the loess. 



It seems likely therefore that the Florencia is a very recent 

 formation in comparison with the Iowan loess. 



The discrepancy observed by Mr. Hershey between his list of 

 Florencia fossils and the published lists of Iowan loess fossils is, 

 so far as generic differences are concerned, merely a matter of 

 nomenclature; the loess lists giving the older generic names, 

 while Mr. Hershey's Florencia list is expressed in the modern 

 generic arrangement. There is therefore no such wide faunal 

 divergence between the two deposits as would appear from Mr. 

 Hershey's remark. 



Academy of Natural Sciences, Philadelphia. 



6. Geology of Franz Joseph Land. — A recent number (Dec. 

 15) of the Quarterly Journal of the Geological Society contains 

 an interesting article by E. T. Newton and J. J. H. Teall, descrip- 

 tive of rocks and fossils from Franz Joseph Land, collected by 

 the Jackson-Harmsworth Expedition. The general results arrived 

 at, which throw much light upon the hitherto almost unknown 



