MARYLAND GEOLOGICAL SURVEY 179 



fusiforme is intermediate both in its genetic relationship and in its 

 morphologic character between spiniger and caricum. It differs from the 

 former in usually possessing a more depressed spire and in having the 

 spiral strife on the upper part of the body whorl more nearly obsolete. It is 

 practically indistinguishable from the yonng of the latter, as would be 

 expected of the ancestral form; but differs from the adult in not attain- 

 ing as great size and in lacking in general those characters which dis- 

 tinguish the adult from the young of that species. Considering the 

 extremely variable Calvert and Choptank descendants of F. spiniger as 

 merely surviving varieties of that Oligocene species, the first appear- 

 ance of F. fusiforme is in the St. Mary's Miocene. Here it shows con- 

 siderable variation ranging on one hand to the short rugose form with 

 a carinated shoulder which Conrad named F. tuherculahim, and on the 

 other to a more elongate form with a smooth, rounded, somewhat 

 polished shoulder which is here treated as an unnamed variety and 

 figured (plate XLV, fig. 3). 



The former died out without descendants at the end of the St. Mary's 

 Miocene; and the latter did likewise, unless F. maximum of the York- 

 town and Duplin Miocene and F. rapum of the Pliocene be considered 

 descendants. 



The typical form of the species, as stated above, is a link between 

 F. spiniger and F. canca, and left in the Yorktown Miocene F. filosum 

 as a descendant, either from which, or contemporaneously with which, 

 appeared the Pliocene to Eecent F. carica. 



Length, 70 mm.; diameter, 36 mm. 



Occurrence. — St. Mary's Formation. St. Mary's Eiver, Cove Point. 



Collections. — Maryland Geological Survey, Johns Hopkins University^ 

 Philadelphia Academy of Natural Sciences, IT. S. National Museum, 

 Cornell University. 



FULGUR TUBERCULATUM Courad. 



Plate XLV, Figs. 4a, 4b. 



Fulgur tuberculatus Conrad, 1840 ?, Fossils of the Medial Tertiary, No. 2, cover. 



(Reprint, 1893, cover of No. 3, p. [80].) 

 Fulgur tuberculatus Conrad, 1842, Proc. Nat. Inst., Bull, ii, p. 185. 

 Fulgur tuberculatum Conrad, 1853, Proc. Acad. Nat. Sci. Phila., vol. vi, p. 317. 

 Busycon tuberculatum Conrad, 1861, Fossils of the Medial Tertiary, No. 4, p. 82, 

 •■■"pi. xlvi, fig. 2. (Reprint, 1893.) 



