MAKINE DIATOMS OF THE PHILIPPINE ISLANDS 155 



SURIRELLA FAUSTA A. Schmidt 



Plate 35, fig 3 

 (Schmidt, Atlas, pi. 4, fig. 20.) 



The deep pits in the ribs of this species are well seen in the speci- 

 mens found, illustrations of which are here given, Schmidt's type 

 figure being rather poor. 



SURIRELLA FLUMINENSIS Grunow 



(Schmidt, Atlas, pi. 5, fig. 6; Peragallo, Diat. France, pi. 60, fig. 1.) 



SURIRELLA GRANDIUSCULA Castracane 



(Castracane, Challenger Exp., pi. 10, fig. 5.) 



SURIRELLA GRAVIS, new species 



Plate 33, fig. 5 



Valve a perfect oval; the rim is heavy, strongly crossbarred and 

 faintly indented, the indentations corresponding with the ends of the 

 ribs or costae; these begin in small but massive knobs elevated above 

 the rim and having a heavy, blunt, process on the outer side; the 

 ribs or costae extend inward from these knobs to the middle and are 

 transverse, except toward the two ends; they are very thin, but 

 deep, and thereby sharply defined; they are widely separated and 

 have between the knobs faintly ribbed scallops next to the rim; a 

 minute angle in each costa near its middle produces a shadowy inter- 

 nal oval, parallel to the margin; the number of costae on each side 

 is the same and they generally are continuous across the valve; 

 there is no median area; the two polar areas of the long diameter 

 are well defined. 



Long diameter 0.079-0.113; short diameter 0.048-0.066 mm. 



The sculpturing of this species is similar to that of the unnamed 

 figure in Schmidt's Atlas, plate 56, figure 6, and less so to S. ayiae 

 Witt (Mus. Godef., p. 114, pi. 15, fig. 4). It is the most massively 

 built Surirella I have seen. 



Type.— Cat. No. 43687, U.S.N.M. 



SURIRELLA HYBRIDA Grunow 



(Van Heurck, Synopsis, pi. 73, fig. 17; Peragallo, Diat., France, pi. 64, figs. 

 1-6.) 



A solitary specimen of this diatom was found by E. Leonard, 

 Liverpool, England, in material supplied by me. Van Heurck in 

 the text of his Synopsis (p. 188) puts this under S. fastuosa Ehren- 

 berg. It is better to hold it separate, as is done by Peragallo. 



SURIRELLA IMITANS, new species 



Plate 34, fig. 4 



Valve circular, rim broad and massive, marked with strong, closely 

 set crosslines and bisected by a median line ; costae beginning with 

 small pentagonal plates elevated above the rim and having four to 



