VMi 



CEYLON MARINE BIOLOGICAL REPORTS. 



justification for placing it only as a form under peltata var. typica, as Weber v. Bosse has done. Var. 

 nummularia, exigua, Sec. should by equal right be included as forms, but Weber v. Bosse has given these 

 a systematically higher rank in calUng them " varieties," i.e., equal with var. typica. 



My contention is strengthened by the fact that O. imbricata itseK shows some variations 

 that could also be classed together. And if we are to place it under any other form it could as well be 

 classed under the small nummularia forms, as for instance /. parvula, as under any of the others. The 

 plausibility is equally great in either case. 



Geographical distribution. — Ceylon : in the upper part of the littoral zone amongst rocks and 

 corals, rather common ; Matara ! GaUe (/. minor) , in many places on the reef (as below the Sailors' Bastion, 

 Star Bastion, Aeolus Bastion, Pigeon Island)! Ambalangoda ! Jaffna! South India: Paumben 

 (/. minor, j. mixta) ! 



18.— CAULERPA PARVULA, n. sp. 



The horizontal axes creeping with their side axes mostly procumbent. The whole plant thus 

 forms mat-like tufts with the assimilation system on one level as in C. nummularia. The assimilation 

 discs very small, about 1 mm., never exceeding 2 mm. 



Under this name I will distinguish a very weak small form in the peltata group which I have observed 

 in several places in the district investigated, and which is figured in figs. 43, 44. The mode of groAvth 

 approaches that of C. nummularia in being richly tufted with the branches procumbent, and all the 

 very small assimilation discs about on the same level, agglomerated together. 



Fig- 44. — C parvula n. sp. (1 x 1). 



Fig. 43. — C parvala n. sp. (1 x 1). 



To judge from the very small dimensions of this plant — the diameter of the assimilation disc 

 about 1 mm. and never exceeding 2 mm. — one might think it to be closely allied to /. exigua, Weber v. 

 Bosse (loc. cit. p. 377 , fig. 1 1 , PI. XXXI.) ; but the character distinguishing this latter — viz. . its assimilation 

 discs as if perfoliate, and situated as it were in one storey above the other — is entirely lacking. But 

 as the assimilation discs are all in their dimensions rather constant, and the plant in other respects as 

 far as its habitat is concerned, makes an impression quite different from C. nummularia, it seems to me 

 to be distinguished as a special form. It forms, one may say, a transition species from the typical 

 nummularia to the imbricata series. For if the side branches, instead of being procumbent were to grow 

 upwards, and if, together with this, the branching were to become radiate, we should have C. imbricata. 



At Paumben, in the Island of Rameswaram, I have also collected some transition forms {C. imbri- 

 cata, /. minor, fig. 40) between this form and C. imbricata. 



Geographical distribution.- — ^Ceylon : Rather locally in rock-pools at Beruwala, and at Paumben 

 in the Island of llameswaram (South India) ! 



