THE NAUTILUS. 101 



little expanded above, thickened and reflexed below. Basal lip with 

 short, white, obtusely triangular tooth, projecting in the plane of the 

 last whorl, not projecting into the aperture. 



Alt. 1.2 ram., diam. 3.5 mm., s. diam. 2.8 mm. 



Four living specimens of this shell were collected. It belongs to 

 the subgenus Perenna Guppy. It is smaller, more depressed, darker 

 in color and with less acute liras than L. lineata. In other members 

 of the lineata group the basal tooth is squarish and projected into the 

 aperture, but in pilsbryi it is broadly pointed and is a continuation 

 of the lower whorl, not projecting into the aperture. 



The slightly reflexed upper margin of the aperture, with no trace 

 of tubercular teeth and the small size of the basal tooth, suggest a 

 very slight immaturity. Possibly a larger series would contain older 

 specimens, which would be found to have upper marginal tubercles, 

 and a more strongly developed basal tooth. In any case the shell 







will be found to be specifically distinct. 

 Types ; No. 22890 M. C. Z. 



NOTES ON MIOCENE CORRELATION. 



BY AXEL OLSSON. 



The deposits which we have come to recognize as of Miocene age 

 on our Atlantic coastal plain differ in many respects from beds of 

 similar age found in other regions. This uniqueness is due to their 

 faunal characteristics, which were developed under conditions of 

 which we have records nowhere else. Therefore, direct correlation 

 or specific identity of forms is possible in only a few cases, and the 

 Miocene age of these beds is based rather more on stratigraphic than 

 on paleontologic grounds. 



The seas of our Eocene and Oligocene periods were rather warm, 

 and hence their faunas find their closest affinities in our present 

 tropical seas. At the close of the Oiigocene, conditions began to 

 change. In the Oak Grove sands of Florida the fauna in a slight 

 way portraits the coming Miocene one. However, more important* 

 of which this special case is but a preliminary result, is the inaugu- 

 ration of a great series of orogenetic movements which culminated 

 in a great series of Miocene uplifts. In Europe the whole series of 



