THE DIATOMACE.E OF PHILADELPHIA AND VICINITY 87 



Karsten states that there are two chromatophores, each of which extends from the 

 middle of one valve to the end and down the middle of the other valve. Mereschkowsky 

 says, however, that there are four plates or chromatophores, sometimes on the valve, some- 

 times on the zone, according to the species, and that two long pyrenoids unite the two 

 opposite chromatophores. 



MASTOGLOIA KINSMANII LEWIS 



Valve lanceolate-elliptical, with sub-rostrate ends; loculi more numerous than in M. 

 angulata but less than in M. apiculata, the middle ones larger. Median line with a sulcus 

 on each side; central area quadrate. 



Mastogloia braunii Grun. (According to Cleve). 



Atlantic City. 



PL 17, Fig. 16. 



MASTOGLOIA EXIGUA LEWIS 



Valve elliptical- or linear-lanceolate; loculi, 2-5, usually 3, larger in the middle and 

 rounded; central space small; striae, 20-24 in 10 ju- 

 Along the coast. 

 PI. 17, Fig. 24. 



MASTOGLOIA SMITHII THWAITES 



Valve lanceolate, sub-rostrate; loculi forming a wide band ending at a distance from 

 the ends; striae transverse, with puncta forming longitudinal rows; central area rounded or 

 transversely elliptical. 



Along the coast. 



PI. 17, Fig. 19. 



MASTOGLOIA LANCEOLATA THWAITES 



Valve lanceolate, with sub-rostrate apices; loculi very numerous; median and central 

 areas indistinct; striae, 19 in 10 /*, punctate, convergent at the ends. 

 Along the coast. 

 PL 17, Fig. 18. 



MASTOGLOIA ELEGANS LEWIS 



Valve lanceolate, acute; loculi indistinct or rudimentary, extending to the ends; cen- 

 tral area apparently quadrate, sometimes indistinct; puncta distinct, 15 in 10 y>, in trans- 

 verse and longitudinal rows. 



Along the coast. Common. 



PL 17, Fig. 20. 



MASTOGLOIA APICULATA WM. SM. 



Valve elliptical-lanceolate, sometimes with slightly produced apices; median line 

 between two ribs; central space very small; loculi numerous; puncta in slightly radiating 

 rows and in longitudinal lines. 



Along the coast. 



PL 17, Figs. 21, 22, 23. 



MASTOGLOIA ANGULATA LEWIS 



Valve elliptical, with produced apices; loculi usually less than 12, unequal, the larger 

 in the middle; striae, 12 in 10 M, puncta in decussating rows. "Differs from apiculata in its 

 more broadly elliptical shape, the smaller number of its loculi and the angular character 

 of its striation" (Lewis). 



