BY G. I. PLAYFAIR. 491 



young form of CI. j)i'onum in which the setaceous beak is not 

 quite formed, the tip acute. Cleve's figure, Sveriges sotvattens- 

 a]g., f.8., shows both these forms together, the lower semicell 

 pronum, the upper elegans. The range of dimensions noted in 

 Australian specimens was : — Long. 159-400; lat. 7-11; ap.circ.2//; 

 with broader specimens of lat. 13-18 intermingled. The latter 

 verged on CI. seiaceurn, but the body proportionately longer, and 

 still the tendency in the inflation to be towards the inner side. 

 Br^bisson's figures work out at about : — Long. 4 54-483; lat.9-13/Li. 

 Raciborski, Desm. Ciast, p. 10, Pl.i., f. 40, gives — Long.314; lat.8; 

 ap. 2fjL — membrana luteola, subtiliter striata. Compare the 

 remarks by Bernard, Protococc. et Desm., p.64, and his figure 

 Pl.i.,f.54. 



Trip, gracile var. suPERBUM(Maskell) Nord., forma. 

 (Pl.xiii., f.26). 



Long. semi. c.sp. 290, centr. 278; lat.bas.c.sp. 60, s.sp. 38/x. 



Botany(2a). 



This specimen I noticed lately in the same sample that yielded 

 Trip, serratran Playf. {ante 1907, Pl.ii., f.2). By comparing it 

 with the latter, the development of the teeth may be observed. 

 From the back of each tooth, a second grows out, the two 

 together forming a bifid verruca (cf. var. ornatum Borge, Austral- 

 sussw., T.4, f.56). The latter may become still more elaborate 

 by growth of additional verrucse; note the three basal verticils 

 in my figure. In a note. I.e., p. 163, on T7-ip. serraticm, I 

 remarked that such a form might develop either into var. 

 sw^e?'6if?n(Mask.) or into var. bidentalum Nord. As a matter of 

 fact it does both. Here we have an example of the former; and 

 lately I noticed a cell of this kind with the teeth of CI. serratiim 

 but drawn out at the tips into aculei in length equal to one-half 

 the diameter of the cell, i.e., nearly twice as long as those in 

 Nordstedt's form. All forms of Tri2)loceras are growth-variations 

 of one species, viz., Trip>. gracile Bailey, 1851, e.g. var. verti- 

 cillatum^aXl., 1848, var. aculeatum Nord., var. bidentatum Nord., 

 var. superhum Mask., var. occidentale Turn., var. hilobatum Turn., 



