MARYLAND GEOLOGICAL SURVEY 271 



Florida, was described by H. C. Lea from the ]\Iiocene of Petersburg, 

 Virginia, as Chiton transenna n. sp. Lea's types which consist of a tail 

 valve and several medial valves, show the identity of the Virginia form 

 with the recent species and with the Maryland fossils. 



Occurrence. — Calvert Formation. Plum Point, 3 miles south of 

 Chesapeake Beach. 



Collections. — Maryland Geological Survey, U. S. National Museum. 



Class SCAPHOPODA. 



OrderSOLENOCONCHIA. 



Family DENTALIID/E. 



Genus DENTALIUM Linne. 



Dentalium attenuatum Say. 



Plate LXIV, Fig. 3. 



Dentalium alteuuatum Saj-, 18:34, Jour. Acad. Nat. Sci. Phila., voL iv, 1st ser., 



p. 154, pi. viii, fig. 3. (Reprint, 1896, Bull. Amer. Pal., No. 5.) 

 Dentalium attenuatum Conrad, 1830, Jour. Acad. Nat. Sci. Phila., vol. vi, 1st ser., 



p. 211. 

 Dentalium dentalis Conrad, 1843, Proc. Nat. Inst., Bull, ii, p. 187. (Not of 



Lamarck.) 

 Dentalium dentale Conrad, 1845, Fossils of the Medial Tertiary, No. 3, p. 78, pi. 



xliv, flg. 9. 

 Dentalium attenuatum Tuomey and Holmes, 1856, Pleiocene Fossils of South 



Carolina, p. 105, pi. xxv, fig. 1. 

 Dentalium attenuatum Emmons, 1858, Rept. N. Car. Geol. Survey, p. 374, fig. 188. 

 Dentalium attenuatum Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 570. 

 Dentalium attenuatum Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), 



p. 14. 

 Dentalium attenuatum Dall, 1893, Trans. Wagner Free Inst. Sci., vol. iii, pt. ii, 



p. 439. 



Description. — " Arcuated ; surface marked with from twelve to sixteen 

 rounded ribs, intervening grooves simple ; lines of growth numerous, 

 distinct; aperture orbicular." Say, 1824. 



Length, 39 mm. ; diameter, 3.5 mm. 



Occurrence. — St. Mary's Formation. St. Mary's River, Langley's 

 Bluff. Choptank Formation. Jones Wharf. Calvert Formation. 

 Plum Point, Chesapeake Beach. 



