MARYLAND GEOLOGICAL SURVEY 215 



Subgenus STHENORHYTIS Conrad. 



ScALA (Sthenorhytis) expansa Conrad. 



Plate LIII, Fig. 7. 



Scalaria expansa Conrad, 1842, Proc. Nat. Inst., Bull, ii, pp. 187, 194, pi. ii, fig. 3. 

 Scala (Sthenorhytis) expansa Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xir, 



p. 565. 

 Scala (Sthe7iorhytis) expansa Meek, 1864, Miocene Check List, Smith. Misc. Coll. 



(183), p. 18. 



Description. — '' Shell acutely ovate, moderately thick, with numerous 

 robust recurved ribs, twelve in number, counting from the summit of the 

 aperture to the reflected lip, inclusive; whirls profoundly ventricose at 

 the sides, somewhat flattened above; four or five in number." Conrad, 

 1843. 



Obsolete impressed spiral lines are sometimes visible between the 

 varices. The number of whorls is sometimes seven. 



Length, 19 mm. ; diameter, 16 mm. 



Occurrence. — St. Mary's Formation. St. Mary's River. Choptank 

 Formation. Jones Wharf. 



Collections. — Wagner Free Institute of Science, Cornell University. 



Scala (Sthenorhytis) pachypleura Conrad. 

 Plate LIII, Fig. 8. 



Scalaria pachypleura Conrad, 1841, Proc. Acad. Nat. Sci. Phila., vol. i, p. 30. 

 Scalaria pachypleura. Conrad, 1843, Jour. Acad. Nat. Sci. Phila., vol. viii, 1st ser., 



p. 186. 

 Scalaria pachypleura Conrad, 1842, Proc. Nat. Inst., Bull, ii, p. 181. 

 Scala {Sthenorhytis) pachypleura Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, 



p. 565. 

 Scala {Sthenorhytis) pachypleura Meek, 1864, Miocene Check List, Smith. Misc. Coll. 



(183), p. 18. 

 Scalaria {Sthenorhytis) pachypleura Conrad, 1868, Amer. Jour. Conch., vol. iii, 



p. 259, pi. xxi, fig. 4. 

 Scala pachypleura Harris, 1893, Amer. Jour. Sci., ser. iii, vol. xlv, p. 35. 



Description. — " Turrited ; short in proportion to. its width ; volutions 

 6 or 7, rapidly diminishing in size ; ribs very thick, prominent, reflected, 

 terminating above in prominent angles. Length five-eighths of an inch." 

 Conrad, 1842. 



The mouth is round or very slightly elliptical. A very distinct basal 



