474 SIBERIAN TROPICAL MIOCENE FOSSII S BALL. 



at the summit and sometimes broken uj* oi- conthicnt on the itosteiior 

 ]>art of tbe shell; also l>y fine I'adiatiii^' stiiu', strongest near the 

 beaks, crossed by obvions inerenient;il lines and nearly or ([nito obso- 

 lete toward the base, in the adult ; the i)osterior fourth of the shell is 

 marked olf from the rest l)y an obscure radial depression which gives 

 the hinder end the appearance of being slightly compressed and 

 twisted to the left; cardinal region beliind the beaks marked by an 

 obscure narrow lanceolate imju'cssed area or escutcheon; hinge with 

 (in the left valve) a large (cartilage i)it, in front of which is a narrow, 

 thin cardinal tooth with an anterior lateral very short and closely 

 adjacent, the posterior lateral also extending but little behind the end 

 of the cartilage pit; interior surface smooth, the pallial line distinct, 

 the sinus broad, bluntly rounded in front and extending to a vertical 

 line dropped from the beak. Lon. of left valve, 33; alt., 30; semidi- 

 ameter of shell, 7 millimetres. 



Two left valves (Mus. Keg. Xo. 478S) were obtained from the bed at 

 Penjinsk Gulf by Dr. Stimpson, in whose honor the species is named. 



This species most closely resembles *S'. modeata A. Adams* from 

 AVest Africa and St. Helena, a s]K^cies whi(!h is somewhat higher, n\ore 

 inflated, with longer lateral teeth, a smaller cartilage pit, and more 

 rounded concentric sculpture. In both the sculpture near the beak 

 tends to be more nearly lamellar and the radiating grooving more 

 l)rominent. 



The nearest relative geographically which ^S*. Stimpsoni \)ossessefi is 

 the similarly sculptured form, refeired to l)y Sehrenk under the name 

 of »S'. c(iJi/ornic((, which is found in the Japan Sea and the Strait of 

 Tartary. AVhile nniny Japanese shells are common to Northwest 

 Anu»rica, it can hardly be said that the identity of this species, which 

 I know only by Schrenk's ligure, with tlu^ (Julf of California shell is 

 fully established. It is possible that onr fossil may ])rovc identical 

 with the living form recorded by Sehrenk, but this can only be deter- 

 mined by a comparison of specimens. 



*Thi8 was referred by Mr. E. A. Sniith, of tlio British Museum, to S. cordifonnia 

 "Chemnitz," which is the West lutliiin and East Amciicau specifs vuriously liiiowii 

 as S. retiviilattt ((jJmel.) Wood, orbiciihil<( aud rtidiala Say, siihtn(»v<ilt( Shy., Jayaniiiii 

 C. B. Adams, and pnlrhelln A. Adams. From those, liowever, the St. Hideua shell 

 is quite distinct, as shown by a scries kindly presented to the National Museum by 

 Capt. Turton. Its sculpture is never sharp and rasjtiufj; to the touch as in the West 

 Indian shell, and all the sitccimens (live) show a minute lunule, under which the 

 shell substan<e is of a deep claret-brown color, forming!; a very c<(ns])icuous spot of 

 color an<l not occurrinj;' in any of the American shells from o\'er tifty different li»i'al- 

 ities. The c(tnceutric ridfjjcs are broad and blunt in tlu^ S. modffitd, wliile they are 

 rcjiresented in the American species only liy thin siiarp lainelhe. As Chemnitz was 

 a biniimial writer only accidentally, and di<l not ailojjt the Einnean system of nom- 

 enclature, his name can not be accepted even for the American shell, which will best 

 be known by the name of Gmelin, adopted and illustrated by Wood, in the belief 

 that the shell is the Telllna reiiculata of Linn(5, a conclusion to which the researches 

 of Hanley on the Einuean types lend a reasonable probability. 



