28 THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 



EUPODISCUS EHK. (1844) 

 (eu, well, pous, a foot, and discus) 



Valve circular, 45-117 M in diam. (De Toni). Central space absent, surface plane with 

 angular cells. At the border short, circular processes or ocelli. 



EUPODISCUS RADIATUS BAIL. 



Valve with radiating hexagonal cells, sometimes slightly curved toward the large ocelli 

 inserted near the border which are hyaline at the centre. Border wide, coarsely striate. 



The number of ocelli heretofore recorded is four. Specimens with five processes are 

 found in the artesian well at St. Augustine, Fla., and in material at Twelfth and Brandy- 

 wine Sts. Mr. Hugo Bilgram has discovered valves with three and six ocelli. 



Not common in the blue clay, but abundant along the southern coast of the Atlantic 

 states and the Gulf of Mexico. 



Not Eupodiscus radiatus Wm. Sm, which is Biddulphia smithii (Ralfs) V. H. 



PL 5, Fig. 3. 



AULISCUS EHR. (1843) 



(aulax, a furrow, referring to the grooves in certain species, according to De Toni, but 

 preferably from auliscos, a small reed, referring to the processes?) 



Frustule cylindrical; zone with longitudinal rows of fine puncta. Valve circular or 

 elliptical, plane except near the processes; central area hyaline, usually circular. Markings 

 of two kinds, granules radiating or scattered and radiating, costate lines, prominent or 

 indistinct. Processes, two or three, large, short, cylindrical, with hyaline surface, near the 

 ends of the major axis in a line oblique to it. 



Auliscus is divided by Rattray into fourteen sections, defined chiefly by the character 

 and arrangement of the markings. About eighty species are described, but as many of the 

 forms are fossil, occuring in the Miocene of California, Oamaru and elsewhere, and as so 

 few species are found in this locality, I shall refer but briefly to this division. 



Striolati. No transverse median areas, striae inconspicuous punctatus 



Lineolati. Markings distinct, pruinose, interrupted pruinosus 



Costati. Transverse median areas usually distinct, markings 



continuous, costate J sculptus 



1 cselatus 



AULISCUS PUNCTATUS BAIL. 



Valve broadly elliptical, or suborbicular, covered with delicate interrupted strise radiat- 

 ing in sinuous lines to the circumference, more evident on the transverse median area; 

 puncta 3 in 10 n, grouped into a rounded area on each side of the median line, elsewhere 

 scattered. Central space rounded, processes two, large, suborbicular. 



Port Penn, Delaware River. Rare. 



PL 5, Fig. 6. 



AULISCUS PRUINOSUS BAIL. 



Valve elliptical, with distinct, interrupted, pruinose, irregular markings diverging in 

 curved lines toward the circumference in the median part and converging toward the proc- 

 esses, interspersed with numerous darker markings having the appearance of apiculi. Cen- 

 tral space nearly circular, sometimes with several granules. Processes large near the ends 

 of the major axis and not oblique to it, or scarcely so, the edges with a crenulate border. 



Blue clay. Rather rare. 



PL 5, Fig. 8. 



