376 ANIMAL NATURE OF DIATOME^. 



EunoticB are never found aduate and parasitic, as is con- 

 stantly the case with the Epithemice. They are all found 

 in fresh water, the greater number are exotic, many 

 rare. When observed laterally, they are frequently 

 seen to be more gibbous or prominent on the dorsum, 

 which proves that the prominences themselves are placed 

 transversely. Thirty-six species are enumerated by 

 Kiitzing. It would seem that he ought rather to refer 

 to the Eunotia formica than to the Epit/iemia gihha, the 

 Eunotia No. 6 (pi. 2, fig. 27 a b,) of Bailey, which has 

 very well-marked transverse strise ; and this uncertainty, 

 were there no other, renders the distinctive characters of 

 the two genera somewhat doubtful. 



3. HiMANTiDiUM. — Lorica in sectione transversali rec- 

 tangula ; strice transversales tenuissimce, densissimce, in- 

 dividua infasciam transversaliter et arete eonjuncta. 



If we could distinguish the Himantidia from the 

 Eunotia by the incomplete division, from which there 

 result associations or polyparies in the form of a band, 

 as in Odontidia and Fragillaria, there would still remain 

 the character of the entire family, i. e. the difference be- 

 tween the two primary surfaces. And since these asso- 

 ciations are not always numerous, as in the three typical 

 species {H. Soleirolii, H. Veneris, H. guyanense), we find 

 it to be justly remarked by Kiitzing, that this genus is 

 not yet well established, a remark that derives increased 

 value from the fact already stated, that there is a lateral 

 association even in the EpithemicB {Epithemia costaia. 

 Men.). This very resemblance, however, attracts atten- 

 tion to another circumstance, viz. the parallelism in 

 the liiynantidia of the lateral surfaces, which, in the 

 Epithemice, are essentially convergent. Of the ten 

 known species, four only are European ; they are all in- 

 habitants of fresh water. 



Of the three genera now enumerated, Kiitzing consti- 

 tutes his family of Eunotiese, which only possess in com- 

 mon the single character of convexity in one and concavity 



