:\r AK^'T, AND (;i:or,of;]r \r, srnA'KY 179 



('(iiiiilv), I''iii'l W'ashiiiLiiiiii. South lki\(M';it iiiuiitli nf Ilroail Creek, Severn 

 IJixcr, l'iscatii\\a\' (('oiiiMd's ori^jiiial locality), "i miles hclow I'otomao 

 Creek. 



Colleciioiis. — ^Maryland ( icoloi^ical Survey, I'liiladelpliia Academy of 

 Natiiial Sciences. Johns llopkins I ' ni versity, U. S. National Museum. 



VEXEiaCAlIDIA .\l.\ltYI-A.\J)irA 11. sp. 



Plate XL, Fi.us. 7, 7a. 



Dcscriiilioii. — Slu'll ihin; ontliiie cirenlar; valves shallow; about 37 

 rihs, hroad and flat on to[), with dee[), nari'ow interspaces near tlie Ijeaks, 

 but very flat, and sq)arated by narrow, impressed line toward the ])eri- 

 phery. 



This species resembles very closely in outline V. pcduncularis from 

 the Paris Basin. It is restricted to the Woodstock substage. 



Length, 80 mm.; width, SO mm. 



Occurrence. — Nanjemoy Foraiation. 2 and 2^- miles above Popes 

 Creek, Popes Creek, Woodstock. 



Collection. — Maryland Geological Survey. 



Vejteeicaedia potapacoexsis n. sp. 

 Plate XL, Figs, -i, 5, 5a, 6, 6a. 



Description. — Shell small, very thick; valves relatively deep, and elon- 

 gate along the line of the beak and posterior basal margin; beak an- 

 teriorly situated; lines of growth strong; ribs 20 to 2i in number, ele- 

 A^ated and crenulated toward the beak, and obsolete toward the 

 periphery; lunule deeply impressed; muscular scars deeply impressed; 

 margin strongly crenulate. 



This form is restricted to the Xanjemoy formation, and is most 

 typically developed in the lower or Potapaco substage. Figure i repre- 

 sents the typical Potapaco form, Figures 5 and 6 show the Woodstock 

 form. 



Length, 40 mm.; width, 33 mm. 



Occurrence. — Xaxjeaigy Foeaiatiox. East and west of Port Tobacco, 

 Popes Creek, Woodstock, ^ mile below Chapel Point, Head of Xanjemoy 



