ARCHEK ON DOCIDIUM PBISTID^E (HOBS.) 83 



narrow, not divided in a dichotomous manner, but by a single deep and 

 wide sinus, the margin serrated ; the two sublobes produced, divergent 

 and tapering, their extremities bi- or tridentate. In the former the empty- 

 frond appears with scattered puncta, in the latter without puncta, but 

 with a marginal series of granules bordering the sinuses. 



It may be, indeed, that I may never have the pleasure to see an 

 actual example of this form, but I must own, nevertheless, that I must 

 for the future (at least ad interim) look upon it in my mind's eye as 

 quite a different thing from M. Americana, and must regard it, not as 

 " var. 6" of that species, but as the quite independent, yet thereto nearly 

 related, species, bearing the (unfortunately rather cacophonous) name, 

 Micrasterias Mahabuleshwarensis (Hobson). 



I now turn to the other form described by Hobson — his Docidium 

 Pristidce. In the month of June last I received from my friend Mr. Kaye, 

 at present resident at Hong-Kong, amongst others, a drawing (Plate II., 

 Tig. 1 ) from the pencil of Dr. Lauder, of a form which I was at once quite 

 disposed to regard as Triploceras gracile (Bailey).* I was somewhat 

 surprised a few days after, on the " Quarterly Journal of Microscopical 

 Science" for July, 1863, making its appearance, to find what I am 

 equally disposed to regard as the same plant described and figuredf as 

 a new species ; but in regard to this, of course, not having seen the 

 actual specimens, I can venture only to offer an opinion. Mr. Hob- 

 son says his plant can hardly be the Docidium (Triploceras) verti- 

 cillatum (Bailey), inasmuch as in the former the teeth are sharp, 

 not obtuse, as in the latter ; and in this I would agree with him, as 

 D. (Triploceras) verticillatum has been more lately restricted by Bailey, 

 in which species the teeth or projections are emarginate. But, I think, 

 if reference be made to Balfs,| Mr. Hobson will find the projections 

 equally sharp at their summits as in his own figure ; and Bailey's figure, 

 clumsy as it is, seems to show the character of the ends more like 

 Mr. Hobson's drawing. Mr. Hobson seems to be unaware that Professor 

 Bailey, apparently quite justifiably from his having seen "great num- 

 bers of each kind," had more lately considered this form as distinct from 

 Triploceras verticillatum, and it is described by him§ under a distinct 

 name, Triploceras gracile. It seems to me, then, that the characters 

 of the body of the frond in both Bailey's and Hobson's forms are alike, 

 and that the only difference lies in those of the terminal processes, which 

 the latter in his description, without any more accurate explanation, 

 merely alludes to as "of very peculiar form," and as " differing greatly" 

 from those of Bailey's form. Judging from the figures only, this diffe- 

 rence seems to lie in the terminal processes of the former being some- 

 what irregularly subdivided, instead of apparently rather regularly three- 



* " Brit. Des.," t. xxxv., 9. c. ; also " Smithsonian Contributions to Knowledge ;" 

 Bailey, "Mic. Obs. in S. Carolina, Georgia, and Florida," p. 38, PI. I., Fig. 10. 

 f " Quart. Journ. Mic. Sci.," N. S., vol. iii., p. 169. 

 X Op. cit., Pt. xxxv., Fig. 9, c. 

 § Loc. cit, p. 38. 



