ORGANOGBAPHIC REVIEW 



OF THE 



GENEEA 0¥ DIATOMEiE, 



ESTABLISHED BY KUTZING. 



1. Epithemia. — Lorica in sectione tj'ansversali trape- 

 zoidea ; strice transversales validce interdum granulatm v. 

 moniliformes. 



The characteristic trapezoidal figure of the transverse 

 section results from the circumstance that the two prin- 

 cipal surfaces are parallel to each other, whilst the lateral 

 ones, again, are more or less convergent. 



The superior surface is convex, the inferior concave, 

 but usually with a much less decided curve ; for which 

 reason they are not exactly parallel. In some species, 

 again, the inferior surface is plane, and the superior 

 strongly convex, and carried down to the lateral surface, 

 whence the section, instead of being trapezoidal, proves 

 semicircular. Besides, the superior surface, instead of 

 being regularly continuous, may present prominent lon- 

 gitudinal costee. At least this is the case in my 

 Epithemia costata, which occurs in Dalmatia, parasitic on 

 Biddulphi(B. {E. major e latere semielliptica apicibus 

 acutis 71011 prominentibus, e facie elliptico elonc/ata, dorso 

 longitiullnaliter costata, costis adlatera transverse striatis.) 

 This species has the form of a grain of coffee applied by 

 its plane surface, and furrowed {solcato) longitudinally 

 along its convex surface. It is 0'043'" long, 0'034'" 

 broad, 0-017'" high. And these longitudinal costse might 

 ■perhaps indicate (accennare) an association of individuals. 



