352 DESCRIPTION OF \_Po7i/ffasirica 



fluent. Diameter l-1008tli. ; forty rays in discs 1-1 152nd, vride ; 

 in a few instances the rays and granules have not run together. 

 Found in dust wafted about in the air. (P. 24, f. 1, 2.) 



DiscoPLEA sinensis. — Margin of disc plane, with equally disposed 

 rays ; central part rather tm-gid and granular, narrower than the 

 Btriated border ; with the striae and granules always separate, and 

 circumscribed by a rim. Diameter 1 -864th. ; ninety-two rays in 

 discs 1-1 152nd. broad; the rays are smooth, not rough as in D. 

 atmospherica. China. (P. 24, f. 4.) 



D. aUantica. — Smaller ; central part rather granular ; rays equally 

 disposed, but not cu-cumscribed so as to represent a rim as in the 

 preceding. (P. 24, f. 3.) 



Genus Endictya. — Lorica bivalve, not in chains, subglobose, no 

 apertui'es on the surface ; valves equal, simply bordered, not con- 

 tiguous nor dentate, but with an intermediate cellular portion. 

 These forms are Coscinodisci, with the discs separated laterally by 

 an intervening cellular structure ; or they may, otherwise, be con- 

 Bidered Dictyopyxides, with the valves not contiguous, but disjoined 

 by the peculiar cellular band named. 



E. oceanica. — Large, disc and sides elegantly but irregularly 

 cellular ; the cells of disc, howe\d, are almost concentric in arrange- 

 ment, and seven in 1-1 152nd. Diameter l-528th. Fossil in African 

 Guano. 



Genus Entomoneis. — Simple, not in chains ; valves equal, quad- 

 rangular, smooth, with a distinct round umbilicus; apertui'es terminal, 

 placed not laterally but quite at the extremities of the truncate ends. 



Entomoncides are smooth Diploneides or JSTaviculae, constricted at 

 ■(he middle, and having true terminal apertures. It differs from 

 A^nyjJiiprora, by the absence of striae. 



E. alata = Navicula alata. — Laterally na\'icular, obtiise ; dorsally 

 deeply constricted at the middle, with wide, truncate extremities ; 

 margin expanded or alate (winged), very transparent, central portion 

 with longitudinal lines; movements active (P. 16, f. 5, 6, 7.) Length 

 J-570thto l-430th. North and Baltic Seas. 



Genus Entopyla (?) Sect. Echinellcea. — Lorica prismatic, com- 

 pressed, multivalve, free, or in chains. Valves straight, contiguous ^ 

 in regular series like the leaves of a book, with a large central aper- 



