Royal Microscojncal Society. 207 



what deeply constricted at the centre, ends subacute, keel mar- 

 fijinal, punctate, length '0055', striae monihform, distinct, about 

 8(D in -001". Fig. 6. 



Bahia, in a gathering made by Captain Perry. The species just 

 described is not uncommon in the Bahia gathering. It differs from 

 N. inlana in the outline of the valve, and also in its much more 

 distinct striae ; it bears some resemblance to N. oUonga, L, W. 

 Bailey,* but is much more deeply constricted, the marginal punctae 

 are also very conspicuous in my species. 



Tryhlionella conspicua, n. sp.,- F. K. — Valve elliptical, with 

 central constriction, ends broadly rounded ; one of the margins 

 punctate, puncta conspicuous, about 12 in "OOl"; centre of valve 

 with a longitudinal elevation gradually sloping towards the margins, 

 striae obsolete. Scrapings from Tredacua shells, West Indies. 



Fig- 7. 



The genera Tryhlionella and Nitzschia contain many forms 

 which seem to combine the characteristics of both genera, 

 Nitzschia? panduriformis and the species above described might 

 fairly claim to belong to the same genus ; both forms possess the 

 longitudinal ridge-like elevation so conspicuous in T. scutelJum; 

 and which Smith, in the Synopsis, describes as a central depressed 

 line. This error arose from the valve he examined lying with its 

 inner surface exposed. The valve when seen with its outer surface 

 uppermost may be likened to a miniature boat upset. Thanks to 

 the binocular the actual form of most of the Diatomaceae may now. 

 be easily understood. 



* See ' Boston Journul of Natural History,' 1SG2. 



