24 THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 



ELABORATI 

 COSCINODISCUS LEWISIANUS GREV. 



Valves elliptical, major axis a little more than twice the minor. From a point, usually 

 near one side, radiate rows of granules in lines nearly parallel to the major axis. Border 

 broad, with distinct striae. 



Great Sedge Island, N. J. (artesian well), and in outcrops later than the Miocene, 

 where it is usually found. 



PI. 3, Fig. 5. 



2. ACTINODISCE^E 



ACTINOPTYCHINjE 



Valves divided into sectors alternately elevated and depressed. 



(1) Actinoptychus. Sectors plane. 



(2) Polymyxus. Sectors convex. 



ACTINOPTYCHUS EHR. (1839) em. V. H. (1890) 

 (actis, a ray, and ptyx, a fold) 



Frustule cylindrical, less in length than the diameter, in zone view undulated. Valve 

 divided into six or more sectors alternately raised and depressed, areolate and punctate, 

 varying in the alternate divisions. The areolation is confined to the outer layer of the valve 

 while the punctation is usually on an inner valve often found detached. Processes on the 

 border, three or more. Umbilicus circular or angular, hyaline. 



ANALYSIS OF SPECIES 



Sectors, six undulatus 



Sectors, eight or more, cellular heliopelta 



Sectors, fourteen, punctate vulgaris 



ACTINOPTYCHUS UNDULATUS (KUETZ.) RALFS 



Valve areolate and punctate in quincunx, divided into six equal sectors, alternately 

 elevated or depressed, their areolations appearing different. Margin well defined. Umbil- 

 icus smooth, hexagonal. Processes three, sometimes six, inserted within the margin of each 

 alternate division. Very variable in size and appearance. 



This is the Actinocyclus of Bailey, figured and described in Amer. Jour. Science, 1842, 

 p. 93, PL 2, Fig. 11, but not named. Kuetzing describes and names it and refers to Bailey. 



Actinoptychus omphalopelta Ehr. 



Actinoptychus cettulosa Ehr., H. L. Smith Sp. Typ., 384. 



Quite common in marine and brackish water and in the blue clay. 



PL 4, Figs. 1, 2, 4 and 6. 



ACTINOPTYCHUS VULGARIS VAR. INTERRUPTA N. VAR. 



Valve with fourteen sectors, the alternate ones divided by a smooth lanceolate space 

 for about one-half the radius, forming with the smooth, circular umbilicus a seven pointed 

 star. The sectors thus divided have coarser puncta in quincunx than the other sectors, 

 ending in a smooth area near the margin, and also larger black puncta scattered from the 

 centre to the semi-radius. 



Near A. vulgaris var. neogradensis Pant. 



Blue clay. Not common. 



PL 4, Fig. 5. 



