MARYLAND GEOLOGICAL SURVEY 151 



SuRCULA BiscATENARiA Conrad. 

 Plate XLI, Fig. 14. 



Pleurotoma catenata Conrad, 1830, Jour. Acad. Nat. Sci. Phila., vol. vi, 1st ser., p. 



223, pL ix, fig. 13. 

 Pleurotoma biscatenaria Conrad, 1834, Jour. Acad. Nat. Sci. Phila., vol. vii, 1st 



ser., p. 140. 

 Pleurotoma biscatenaria Conrad, 1842, Proc. Nat. Inst., Bull, ii, p. 186. 

 Surcula biscatenaria Conrad, 1863, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. .561. 

 Surcula biscatenaria Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 20. 

 Not Pleurotoma catenata Lamarck. 



Description. — " Shell subf usiform ; with two approximate chainlike 

 or nodose caringe on each whorl; the large whorl with strong revolving 

 and intervening finer striae; spire elevated, conical; whorls concave on 

 the upper part; beak slightly recurved. 



" The carinas upon the whorls of the spire are placed nearest the base : 

 the old shells of this species become quite thick, and have the right lip 

 much arcuated; the spire occupies about half the length of the shell." 

 Conrad, 1830. 



This species has the deep, narrow, sharply incised notch of a true 

 Pleurotoma, but the notch is distinctly above the shoulder near the center 

 of the subsutural concavity. 



There are specimens in the National Museum which probably belong 

 to this species, although they may represent a variety. The only differ- 

 ence of these forms is that the notch is somewhat less sharply incised. 



Length, 40 mm.; diameter, 15 mm. 



Occurrence. — St. Mary's Formation, St. Mary^s Eiver. Chop- 

 tank Formation. Jones Wharf. Calvert Formation. Plum 

 Point (?). 



Collections. — Maryland Geological Survey, Johns Hopkins University, 

 U. S. National Museum, Cornell University. 



Surcula engonata Conrad. 

 Plate XLI, Fig. 15. 



Surcula engonata Conrad, 1862, Proc. Acad. Nat. Sci. Phila., vol. xiv, p. 285. 

 Surcula engonata Meek, 1864, Miocene Check List, Smith. Misc. Coll. (183), p. 21. 

 Not Cochlesprra engonata Conrad, 1865. 



Description. — " Fusiform ; whorls 8, turrited, nodulose on the angle, 

 very minute revolving lines above the angle, distinct below it; one line 



