THE DISTRIBUTION OF LOESS FOSSILS I 3 I 



Altitude about 170 feet. A small collection containing species 

 1 1 and 30 was made. 



e. A locality in the northwestern part of Fairmount Park on 

 a northerly slope, somewhat grassy, but with shrubs and a few 

 bur oaks, nearly opposite 8th avenue. Altitude 280 to 300 feet 

 above the valley. Here were found species 3, 8, 11, 13, 18, 19, 

 and 27, and also one specimen of Bifidaria procera, the only 

 recent species found in the tract examined, which was not found 

 in the loess. This locality is just over the brow, on the north or 

 leeward side, 1 of one of the most exposed ridges in the area 

 under consideration. 



/ A part of the same slope immediately below e, and 50 to 

 100 feet lower. Here the forest is better developed and con- 

 tains a number of species of trees. Species 8, 11, 18, 19, 22, 

 25, and 28 were found. The points e and / are on the same 

 very steep slope, but e is much more exposed and drier,/ beino- 

 more protected by its forest covering and position. A compari- 

 son of the species from these points is therefore interesting. 

 Species 3 and 13, while common at e were not found at /, the 

 lower point. While 18 was common at e, only one specimen 

 was found at / No. 19 is also more common at e than at / 

 These facts are of interest when we seek to determine the extent 

 to which shells are likely to be washed down even very steep 

 slopes. Nos. 8 and 1 1 were about equally abundant, while Nos. 

 22, 25, and 28 were found only at / 



g. The banks and grassy slope near and above the exposure 

 M. This yielded species 3, 13, 21, 24, and 27. 



It will be observed that species 1, 2, 4, 5, 6, 7, 9, 12, 14, 15, 

 16, 17, 20, 23, and 26 — or just one half the total number — are 

 not contained in the collections of modern shells cited. The 

 number of individuals of the surface species is also compara- 

 tively small. Of these numbers, 1, 16, and 23 are extinct in 

 that section of the country, No. 1 occurring eastward, No. 16 

 westward, and No. 23 being entirely extinct. 



'The prevailing winds during the seasons of the year when the snails are active, 

 are from the southwest. 



