THE YAN YEAN RESERVOIR, VICTORIA. 55 
appear to be founded mostly on inaccuracies of observation and drawing. 
Triploceras gracile certainly exhibits the widest range of variation of any 
known Desmid, and confusion has always existed as to which form, if any, 
should be regarded as the type-form. 
The form described and figured as “ T. gracile, forma ” in the Trans. Linn. 
Soc. ser. 2, Bot. v. (1896) p. 236, t. 13. figs. 9-13, is the generally-distributed 
form in the United States, occurring from Maine to Florida. Bailey’s original 
specimens were also collected in the eastern parts of the United States, and 
it is therefore highly probable that they were in no way different from this 
form. In fact, a close scrutiny of Bailey’s figure, although a wretched 
drawing, confirms this opinion. Moreover, precisely the same form occurs 
in Central America, India, Ceylon, and Queensland. Taking all these facts 
into consideration, there is every reason for regarding this form as the 
type-form of the species *. The characters of importance of this form, which 
I shall henceforth consider as the type-form, are the whorls of acuminate 
verrucæ and the peculiar apical lobulation. The apex of each semicell is 
slightly flattened and is furnished with two divergent processes, somewhat 
obliquely disposed and bispinate (rarely trispinate) at their extremities. 
Alternating with these processes are two shorter apical lobes each of which 
terminates in an upwardly-curved spine. These more rounded lobes some- 
times possess a subsidiary papilla (or even a spine) below the terminal one, 
and the relative proportions of the two spinate processes vary much. These 
variations, which are shown in the accompanying figures (text-fig. 7, A & B), 
in no way affect the distinctiveness of the apical characters. The number of 
Fig. 7. 
NJ 
A pices of two semicells of the type-form of Triploceras gracile, Dail. 
In B the obliquely disposed processes are shorter and broader than in A. 
a, front view ; 5, apex seen from the vertical view ; c, side view. АП x 500. 
whorls of acuminate verrucæ on а semicell is very variable (9-16), and the 
acuminate apices of these warts often graduate into shortly spinate apices. 
These are the limits of variation I have noticed in the type-form. Most of 
* Dr. О. Borge has also regarded this form as the type. Cf. Borge, in Bih. till K. Sv. 
Vet.-Akad. Handl. xxii. по. 9 (1896), p. 28, t. 4. fig. 57. 
