431 DESCEiPTioN OF [Polj/ffastrica. 



at the border extensively and minutely cellular ; the centre of disc 

 broad, but cii'cumscribed and punctate. Has the habit of Coscinodiscus 

 dkciger. Diameter 1 -648th. Yii'ginia. 



Pyxidicula (?) Actinocycltis. — Testules with two flattened, finely cel- 

 lular, and elegantly radiated patellse , rays thii'ty-nine, straight and 

 dense, reaching the centre. Diameter 1- 720th. Richmond, Vii-ginia. 



P. gemmifera. Habit of Coscinodiscus. — Testules with turgid, 

 crystalline patellae, not bordered ; with lax rows of crystalline nodules, 

 fifteen of which nearly arrive at the centre. Diameter 1.864th. 

 Maryland. 



P. (?) hirsuta. — Subglobose, not cellular; with simple indistinct 

 furcate hairs. Diameter 1-11 5th. Maiyland. 'Rahit oi Xanthidium, 

 but cleft into two patellfe. 



P. limhata. — Oblong, with a central keel ; patellae in front with 

 a central cellular surface, and thirty-two to forty radiating lines ; 

 border not cellular. Diameter 1-79 2nd. Maryland. 



P. 2Jr(ef<^xta. — Patellae two, not cellular, nor radiated, but with the 

 border extending fi-om the central area, overspread with rough points 

 (hispid.) Diameter l-1152ud. ^gina. 



P. (?) urccohs. — Patellae two, unequally urceolate ; one elongated and 

 more convex ; the other shorter, extended on each side into a 

 flattened margin; no cells, but smooth; ten rays in the long patella, 

 and eight in the shorter, in the former smooth, in the latter apiculate. 

 Diameter 1-1 728th. Eichmond, Virginia. See Xanthiopysis. 



P. cristata. — Lenticular, patellar two ; no distinct rim, but a 

 slightly prominent suture between the two contiguous patella? ; disc 

 cellular; cells in rows. Diameter 1-8 16th. Eichmond, Virginia. 

 P. dentafa. — Convex, with a slightly dentated margin ; teeth 

 irregular, with very large cells, 6 in l-1200th. Diameter l-840th. 

 Antarctic Ocean. 



P. longa. — Oblong ; its length two-and-a-half times greater than 

 its breadth; cylindrical; apices rounded; suture longitudinal. 

 Length l-1080th. Fossil, Virginia. 



P. decimata. — Pound in the chalk marl of ^gino. 

 P. heUenica. — From the same locality. It = coscinodiscus crucia- 

 im (Kiitz.) and probably is Dictijopjxis Rellenica (Ehr.) 



