m
Dr. Balfour. Aberdeenshire, Dr. Dickie. Pass of Killiecrankie, Mr.
P. Grant. Ben Lawers, elev. 1700 feet, Aug. 1855, Dr. Arnott. Perthshire,
Dr. Greville.
I first detected this interesting species in gatherings made by Dr. Balfour
iu the above localities, aud subsequently found it in collections of Dr. Dickie
and Mr. P. Grant, which have been iu my possession for several years. Dr.
Arnott and Dr. Greville have since supplied me with specimens from other
localities. In every case the form is, however, very sparingly distributed
amongst other Diatomaceæ, and in no instance have I seen it in a fresh or
living state. In ignorance of its general habit and character, not even certain
to which subtribe it properly belongs, I am unable to determine its generic
position, and am obliged to place it with those species to which it most nearly
approaches in the structure of its frustule. These certainly are the species
included under the present genus, its frustules being annulate aud definite,
and the septa opposite. Should a further acquaintance with the species in a
living state enable me to place it with confidence among those forms that
unite after self-division into a zigzag chain, I know of no character that would
separate it from Grammatophora. The absence of a curve iu its septa, relied
upon by Dr. Greville, I cannot regard as of sufficient importance to constitute
a generic distinction, as this feature is scarcely noticeable in some states of
G. macilenta (see Plate LXI. 382), and is uniformly absent in G. stricta,
Ehr. (see Kiitz. Bacill. xxix. 76).
If, however, future observation require the separation of the present species
from the genus Grammatophora, I must at all events deprecate the adoption
of the name Diatomella, as contrary to a canon of nomenclature now, I
believe, generally received, viz. “ Generic names are inadmissible that are
founded upon a resemblance to other genera, and which express this resemblance
by diminutives, or by syllables, either prefixed or added.”—
DeCandolle, Théorie Elém. Part III.
Supp. Plate LXI. 383.
G e n u s 44. TABEL LARIA, Ehr.
Frustules oblong, cohering into a zigzag chain, annulate ; septa alternate,
entire, direct ; valves linear, inflated at the centre and extremities,
striated.
The annulate frustules and inflated valves distinguish the present
genus from Diatoma, and the alternate septa from Grammatophora.
Professor Kützing has described three recent species of this genus,
finding a character for one of these in its opposite “ vittæ,” and
distinguishing the other two by the circumstance of the one having
its valvular inflations of equal size, and the other having the central
inflation larger than the terminal enlargements. I cannot accept any
of these characters as a sufficient specific distinction. In all the
specimens I have examined, and it will be seen how widely these
have been collected, I find alternate septa. The alternate character
is distinctly obvious to the eye in T. flocculosa ; but that their position
and character are precisely similar in T. fenestrata, must I think be
apparent by an examination of the analyses given in Plate X L III.
31 6 t & 3 l 7t ; in both, the septa are confined to one extremity of
each annulus, and must therefore in both be really alternate.
With regard to the character on which Kützing reties as separating
his T. ventricosa from T.flocculosa, viz. the relative sizes of the central
and terminal inflations, I have only to say, that, in the numerous
specimens in my possession, I find these characters exceedingly
variable, and in no case have I met with valves in which the central
does not in some degree exceed the terminal enlargements.
I therefore feel myself obliged to unite all these specimens under
one designation, and, although the specific name of ventricosa may
be the more appropriate one, must adhere to the term which has
priority and almost universal usage in its favour.
1. T a b e l l a r i a flo c c u lo sa , Kiiir. Frustules indefinite; septa from
3 to 5 from each margin, slightly unequal. Length of frustule
•0006" to -0016". Valve with the central inflation the largest ;
striæ indistinct, about 36 in -OOl". v.v.
Kûtz. Bacill. xvii. 21. Raben. Süssw. Diat, x. 2. Hass. Alg. xciv. 9. Ta-
hellaria ventricosa, Kütz. Bacill. xxx. 74. Raben. Snssw. Diat. x. o.
Conferva flocculosa, Dillw. Conf. xxviü. ? BaciUaria tahelBiris, Lhr.
Inf. XV. / . Biatoma Jiocculosum, Lyng. Tent. Ixi. B. 4 i Ralis, Ann.
vol. 11. pl. LX. 3. ad specim. authen. in herb. Jenn.
Fresh water : frequent in boggy pools. Wareham, Dorsetshire, Dec. 1849 ;
Plumpton, Sussex, May 1853; Grassmere, Westmoreland, and Rackham.
Sussex Aug. 1853 ; River Lee, near Cork, April 1855, W. Sm. Jackswood,
and Coldbath Springs, Tunbridge Wells, Dec. 1842, Mr. Jenner. Lancashire,
March 1852, Mr. Johnson. Aberdeenshire, Dr. Dickie. Ben M° Dhui, elev.
3840 feet Mr. P. Grant. Woodhead, Cheshire, IMay 1853, Mr. T. Brittain.
Isle of Arran, July 1853, Dr. Arnott. Ben Lawers, Aug. IWo?., Professor
Williamson. Braemar, Aug. \%5A, Dr. Balfour. Lough Mourne, Peterhead,
and Lough Island Reavey Deposits. (Falaise, M. De Brébisson. Lac Guery,
Mont Dore, elev. 4062 feet, June 1854, W. Sm.)
Plate XLIII. 316.