Species of Diatoms from Hongkong. 3 



Frustules nearly, but not fully, hemispherical previous to self- 

 division ; on one side plane, with an axis through the middle 

 and a valve on each side; on the convex surface marked with a 

 middle longitudinal line and two fainter ones, indicating the 

 direction of future tissiparous division. The valves lunate, with 

 a straight ventral margin and obtuse ends ; the surface covered 

 with very fine lines of hexagonal cellulation, radiating from a 

 blank nucleus or roundish vacant space, not situated exactly in 

 the centre, but a little towards the ventral side. Radiating from 

 the same point, and at more remote intervals, are also exceed- 

 ingly fine, but stronger, lines or delicate costse, which terminate 

 in a continuous row of punctiform nodules a little within the 

 margin of the whole circumference. 



The first gatherings of Diatoms in Hongkong Harbour, sent 

 me by Mr. Palmer, contained some imperfect frustules of this 

 Diatom, which, along with his notes and sketches, greatly stimu- 

 lated my desire for more perfect materials. Fortunately my 

 friend Mr. L. Hardman had also received some collections from 

 the same locality; and, as they were rich in this production, he, 

 at my request, most kindly instituted a careful and minute 

 examination into its structure ; and it is only due to his friendly 

 aid and unrivalled manipulation to state that it is mainly from 

 his notes, sketches, and specimens that my drawings and de- 

 scriptions were prepared. My valued correspondent Mr. Palmer 

 subsequently forwarded a cell filled with frustules, preserved in 

 fluid, along with additional interesting information confirming 

 the results at which both Mr. Hardman and myself had arrived. 

 It is with sincere pleasure that I unite with the name of the 

 discoverer, now so worthily bestowed on the genus, that of the 

 gentleman who so materially aided me in the investigation of 

 its structure. 



Palmeria Hardmaniana is a very delicate and fragile Diatom, 

 readily dividing (if arrived at the proper stage) at the slightest 

 touch — falling asunder as the segments of an orange are sepa- 

 rated, to use a simile already referred to. In size the frustules 

 appear to have a great range. Mr. Hardman has observed some, 

 however, which seem to belong to a second species, only half 

 the average size of the one now described, and much stronger 

 and thicker. As far as I can judge from a specimen he has 

 kindly given me, I am disposed to agree with him ; but it will 

 be well to examine a larger series of examples before coming to 

 a positive conclusion. Mr. Palmer informs me that he also has 

 observed frustules of a much smaller size ; but, in the absence 

 of details, it is impossible to say whether they belong to the 

 supposed new species or not. 



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