66 LAND AND FRESn-WATER SHELLS OF N. A. [PART IV. 



124) is veiy poor, and in fact looks mucli like the young of 

 P. 2)onderosum. 



10. P. ponderosum, Say. 



Melanin ponderosa, Anthoxy, Proc. Acad. Nat. Sci., Feb., 18G0, p. 59. Btnney, 



Check List, No. 21.3. BuoT, List. p. 59. 

 Trypnnostoma dux. Lea, Proc. Acad. Nat. Sci., p. 170, 18G2. Jour. Acad. Nat. Sci., 



V, pt. 3, p. 283, t. 3G, f. 105. Ob.4., ix, p. 105. 



Description. — Shell conic, broad, smooth, olivaceous, thick; spire 



considerably but not acutely elevated ; whorls 7-8, subconvex ; lines 



of growth curved and strong ; sutures distinct ; aper- 

 Fig. 128. ^ =" ' ^ 



ture rliombic, rather small, whitish within ; columella 



indented, outer lip much curved forward, forming a 



broad, well marked sinus at base. 



Habitat. — Tennessee. 



Observations. — One of the most ponderous of the 



genus. In form it resembles it/, canaliculata, Say, but 



has not the channel of that species, and differs also in 



the apertui'c. The body-whorl is strongly keeled about 



the middle, and has another and less clearly defined 



carina about midway between the first and the suture 



above. The lines of growth are very strong and occasionally varicose. 



A strong deposit of white callus is found upon the columella, which 



is much thickened near the hasQ.— Anthony. 



At a meeting of the New York Lyceum of Natural History 

 held in June, 1860, Dr. Budd referred this species to Mr. Con- 

 rad's excnrata. I have already remarked upon the resemblance 

 in the description of the latter species. There can be no doubt 

 that Mr. Lea's T. dux is a synouyme. Mr. Lea's description 

 here follows. The figure of ^^onderosct is from the original 

 type, that of dux is copied from Mr. Lea's. 



Trypanostoma dux. — Shell carinate, pyramidal, thick, reddish- 

 brown ; spire much raised ; sutures slightly impressed ; whorls about 

 nine, flattened; aperture rather large, rhombic, pale salmon-color 

 within an'd very much twisted. 



Operculum subpyriform, dark brown, with polar point near to the 

 basal line. 



IZaftito^— Tennessee Iliver; Dr. 'W. Spilhnan : Fox River, Illinois; 

 J. Sampson ; Oostenaula : Rev. G. \Yhite : Tuscumbia ; B. Pybas. 



Diameter, -75; length, 1-80 inches. 



