350 DEscEiPTioN OF \JBolygasirica. 



external portion or margin of the disc not being cellular, and from 

 the latter by the absence of a distinct margiaal figured zone 

 or rim. 



DiCTYOLAMFEA &tella. — Characters unknown. 

 - Genus Diploneis. — Vide Pinmdaria. 



Genus Discoplea (Ehr.) — Characters unknown. 

 This genus has a close affinity with Pyxidicula; it is in part 

 equivalent to Ci/cloteUa (Kutz.), (p. 341,) one of the two sections of 

 which, in this author's system, distinguished by being included 

 in a gelatinous mass or nidus, has, indeed, the term Discoplea 

 applied to it. 



D. (?) grceca. = Coscinodiscus (?) grcemts (Kiitz.) Disciform, on 

 plane sides, interruptedly striated in a radiating manner. Diameter 

 l-864th. In Greek marl. 



D. Kutzingii. — Smaller, disciform ; radiant strise present only 

 along the margin of the plane sides. 



D. dendroclmra. — Small, tumid in front ; margin of disc, and also 

 the centre, smooth ; the latter, however, with a minutely striated 

 ring siu-rounding it. The rays of the central coronula (circlet) about 

 ten in number. Diameter 1- 1920th. Found on the roots of plants 

 from the moimtains of Venezuela "* Habit of D. compla. 



D.(:)A7ne)'ica>ia. — Turgid, with the habit of a compressed Gallionella 

 or Pyxidicula ; the dorsum with thi^e ti'ansverse keels ; the lateral 

 disc dotted in the middle. Diameter 1-6 60th. Yirginia, Maryland. 

 D. (?) Actinocyclus = Pyxidicula (? ) Actinocydus. 

 D. (?) astrcea. — Large, flat ; lateral margin densely rayed ; centre 

 dotted. Diameter l-636th. Kurdistan. It has the habit and 

 size of GaJUoneUa vUrians, with the peculiar central granules ; but 

 not being met with in chains, seems nearer Disco2)lca. 



D. (?o/«^^^^— Slender, tumid in front; a crown of striae on the side 

 near the margin ; and a remarkable central agglomeration of granules. 

 Habit of D. Americana, but smaller. 



D. denticulata Surface beset with a pecuKar, straight, and parallel 



row of small cells or granules, ten La 1-1 152nd; margin dentated. 

 Diameter 1-6 72nd. Bermuda. In the character of its margin it 

 resembles Gallionella sxdcata, bat by the cells of its disc approaches 

 Coscimdiscua Uneatm. 



