HANNA: MIOCENE LAND SHELLS. 5 



able to detect any other difference." (Proc. Wash. Acad. Sci., 

 vol II, p. 657, 1900.) 



The University of Kansas expedition secured two specimens 

 of this interesting form and although they are not perfect I 

 am able to point out specific differences which are of sufficient 

 importance to continue the separation of the fossil from the 

 living form. Comparison has been made with several fossil 

 specimens in the collection of the University of California; 

 also with 16 excellent specimens of Ammonitella yatesi Cooper 

 from the Hemphill collection which now forms a part of the 

 museum of the California Academy of Sciences. The recent 

 shells came from "near Murphys, California," and were col- 

 lected by Henry Hemphill. 



One important difference is in size. The largest yatesi is but 9 mm. 

 in greatest diameter, whereas the largest Innata (and it is imperfect) 

 is 15 mm. The former also has eight whorls while the latter has nine. 

 The umbilicus of liinata is proportionately wider and the apex is a hol- 

 low cone. The apex of yatesi is truncated inside and therefore shallower. 

 On the ventral side of yatesi the last whorl swings out over the one pre- 

 ceding, but this is not true in the best specimen of lunata, although figure 

 1 of Stearns (White) indicates that there may be some variation in this 

 respect in the fossil species. 



MEASUREMENTS. 

 (All measurements are in millimeters.) 



A. iiatesi. , A.hdiata. , 



Greatest diameter 9 . 00 15 . 00 12 . 50 



Least diameter 8 . 00 13 . 50 11 . 00 



Greatest altitude 4.50 7.50 6.50 



No measurements of the fossils studied by Conrad, Stearns 

 and White have been published. Their figures show that the 

 shell substance of the body whorl has been lost, a condition 

 which is almost always the case. The University of Kansas 

 specimens are in that condition, but through the kindness of 

 Prof. Bruce L. Clark, I was permitted to examine well-pre- 

 served material in the University of California. It was learned 

 that the shells are smooth and shining as in the recent species, 

 with growth wrinkles barely showing on the latter part of 

 the body whorl. 



Gastrodonta imperforata Hanna. New species. 



(Plate I: figures 1, 2. O.) 



Whorls six; spire high and dome-shaped; sutures moderately im- 

 pressed; apex marked with fine regular growth lines; growth lines on 

 the body whorl slightly uneven but without an approach to a ribbed con- 



