322 NEW MICROSCOPIC ALG.E. 



Society of London" (vol. vi., p. 12.) Many of these had been 

 gathered by T. A., and ascertained by him to be undescribed long 

 before their publication in the work alluded to. 



Sonne there were, however, which a glance sufficed to show, 

 new and undescribed. Of the first two species of Diatomaceae 

 now to be named, and a Desmid to be presently mentioned, an 

 account was given to the Microscopical Society of London, and 

 inserted in their " Transactions" (vol. viii., p. 147.) 



The first of these is there named, and thus characterized — 



PODOSIRA (?) COMPRESSA, n. sp. T. W. (PL XVL, fig. 7.) 



Frustules geminate, polar always much shorter than the 

 equatorial diameter; valves elliptic, indistinctly marked with 

 scattered puncta; cingulum smooth. Breadth of long diameter 

 of valve, -0008 to -0014; of short diameter, '0004 to -0005. 



" This interesting form has, I believe, only been met with as 

 yet on the coast of Northumberland, where it was found by Mr. 

 Atthey, along shallow sand — ripples at Druridge Bay, and subse- 

 quently on Cresswell sands. 1 have seen specimens from the 

 latter habitat, collected by the Rev. Robert Taylor. It occurs 

 plentifully, never more than in pairs of frustules ; always per- 

 fectly free, on the sands; and is, when dry, of a clear brown 

 colour. In deference to the opinionof my friend, Mr. Roper, this 

 was placed provisionally in the genus Podosira, though I cannot 

 but think it has little right to be there, and that a new genus 

 should be constituted for it ; the compressed valves, entire absence 

 of stipes or attachment of any kind during growth, and want of 

 thickened umbilicus, furnishing valid and sufficient grounds for 

 such separation. Perhaps Coscinodiscus ? ovalis, and some other 

 oval and elliptic forms (of which I am acquainted with several, 

 chiefly from ' Bermuda Earth'), might be associated with it to 

 form such proposed new genus." 



It is unfortunate that the wanton erection of trivial varieties 

 of form into species in this tribe has prevailed to so great an ex- 

 tent ; had it been otherwise, I should unhesitatingly have con- 

 stituted a new genus for this interesting form, being fully satis- 

 fied of its right to such rank. 



