1922] Fauna from the Eocene of Washington 41 



Original description. "Shell, small, with five whorls, the first two, turbinate, smooth ; 

 the third whorl is cancellated by ten or twelve ribs. About every fourth rib is enlarged. 

 These heavy ribs are well rounded on the fourth and fifth whorls and are more oblique 

 than those on the third. They extend from an indistinct, irregular suture over the entire 

 w r horl. Strong revolving ribs with finer riblets also decorate this beautitul little shell. 

 Mouth, sub-oval ; outer lip thickened, rounded, and crenulated on interior. Columella 

 marked by three strong plaits, the posterior one being the strongest. Canal short and very 

 slightly notched. 



Dimensions. Length, 12 mm. ; width of body-whorl, 6 mm." 



The type locality of this species is on the west side of Marysville Buttes, 

 California (University of California, Locality 1853). Dr. Dickerson also states 

 that a specimen was found near Fort Tejon, California, and he later lists it from 

 south of Mount Diablo, the Coalinga District, and San Diego. 



In Washington it occurs abundantly at locality 329, on the Cowlitz River, 

 and also from several other localities in the western part of the state. 



After careful examination, the specimens from Washington appear to be 

 the same as the California species. The majority of the northern specimens 

 attain a larger size than that given for the type in California. The adult specimens 

 have from 10 to 12 longitudinal ribs on the body whorl. The younger and more 

 immature shells possessing an average altitude of 10 mm. have from 14 to 16 

 longitudinal ribs on the body whorl. These ribs on the younger forms are not 

 as well developed in size and character as on the more mature specimens. Every 

 fourth rib may or may not become enlarged into a varix. Other characters are 

 as described by Dickerson for the species stantoni. 



As far as the details of the shell are concerned A. stantoni shows a very 

 close resemblance to Admete evulsa (Solander) from the Bartonian of England, 

 and the Paris Basin. Illustration PI. XI fig. 7 has been inserted for comparison. 

 The nearest noticeable difference between the two species is the absence in A. 

 evulsa of finer, interstitial threads between the larger revolving ribs. 



A comparison made with specimens of Admete tortiplica (Conrad) in the 

 Paleontological collections at Cornell University from the Sabine Eocene of 

 Wood's Bluff, Alabama, show somewhat a close relationship. A. tortiplica shows 

 considerable variation in the sculpture of the revolving ribs and threads. Some 

 possess the ribs without the intervening threads as in the case of A. evulsa, while 

 other specimens have the threads well developed as in the case of A. stantoni. 

 The sculpture on A. tortiplica is much stronger and sharper than on A. evulsa 

 or A. stantoni and the whorls are less ventricose. 



Dimensions. Altitude 18 mm. ; width of body whorl 10 mm. ; apical angle 

 55. (Measurements taken on a large specimen.) 



Occurrence. At locality 329 (University of Washington Palaeontological 

 Collection) west bank of Cowlitz River, near Vader, Lewis County, Section 28, 



