MARYLAND GEOLOGICAL SURVEY 493 



The form as figured represents a well-developed specimen, but irregu- 

 lar and much smaller forms are frequent. It differs from B. americana 

 (Ealfs) in the pearly character of the puncta and in the undulations 

 of their rows. It is typical of the entire Miocene deposits of the eastern 

 states and occurs rarely in the deposits of Oawain, New Zealand and in 

 the var. neogradeuse Grunow has been noticed in the Hungarian de- 

 posits. 



Occwrrertce.— Calvert Formation. Flag Pond, f mile south of 

 Parker Creek, 3 miles north of Parker Creek, Plum Point, -J mile north 

 of Forest Wharf, Nomini Bay, Chesapeake Beach, God's Grace Point, 

 Fairhaven, 1 mile west of Tracy Landing, l^ miles southeast of Mar- 

 riott Hill, 1 mile north of Jewell, 1 mile north of Jones Point, 1 mile 

 south of Chesapeake K. E. Bridge, 1 mile northwest of West River, 1 

 mile east of Marriott Hill. 



Collection. — Maryland Geological Survey. 



Biddulphia cookiana Kain and Schultze. 



BiDDULPHiA DECiPiENS Grunow. 



Plate CXXXIV, Fig. 8. 



Biddulphia decipiens Van Heurck, 1881, Syn. Diat. Belg., pi. c, figs. 3, 4. 

 Amphitelra>i {Biddulphia) alt€na7is, H. L. Smith, 1887, The Microscope, p. 67 (with 



fig-)- 

 Biddulphia decipiens Boyer, 1901, Proc. Acad. Nat. Sci. Phila., vol. lu, p. 716. 



Description.— ValYe rhomboidal, with the sides turgid and produced, 

 giving, therefore, a cruciform outline. Surface rising suddenly from 

 near the margin into an ellipsoidal elevation, the major diameter of 

 which is at right angles to the major axis of the valve, with hexagonal 

 reticulations, about 5 in .01 mm., at the center, from which they radiate 

 toward the processes and rounded angles of the sides where they are 

 about 9 in .01 mm. Processes inflated at the base, small and obtuse. At 

 the margin of the elevation, placed obliquely on each side, a strong spine 

 projects. The figure represents a smaller but more common form. 



Occurrence.— Caj^ybrt Formation. Marriott Hill, God's Grace 

 Point, 1 mile north of Jones Point. Not uncommon. 



Collection.— MaTjlandi Geological Survey. 



