330 CEYLON PEA.RL OYSTER REPORT. 



genus to such forms. I prefer, therefore, to retain the old generic title in that sense 

 and to add the word " unisexual" before " polycarps" in the definition. "MICHAELSEN'S 

 Gynandrocarpa, as he first defined it, would then be the corresponding genus 

 containing those species which have hermaphrodite polycarps. More recently 

 (' Mitth. Naturh. Mus. Hamburg,' XXI.) MICHAELSEN has introduced still further 

 generic sub-divisions of Gynandrocarpa based upon details of arrangement of the 

 reproductive organs which seem to me to be of only specific value. If similar details 

 were to be recognised in the genera Styela and Polycarpa almost every species would 

 become a separate genus. 



Gynandrocarpa nigricans, SLUITEE. 



This is a. very dark coloured species which the " Siboga " found at the Island 

 Sarassa, in Malaysia, at a depth of 16 fathoms. Our Ceylon specimens were from 

 Talaivillu Paar, in the Gulf of Manaar, where we obtained a number of colonies from 

 6 centinis. x 3 centims. downwards, in size, growing over coral and shell fragments. 

 The ascidiozooids are very closely placed, there being little or no common test except 

 at the edges of the colony. The general appearance of the animal when alive is black 

 and white, the parts that are not deeply pigmented being transparent. 



The arrangement of the vessels in the branchial sac and other points in the 

 internal structure agree with SLUITER'S description. The darkly pigmented blood 

 channels in the marginal parts of the colony are a remarkable feature in this species. 



Gynandrocarpa (Eusynstyela) imthurni, n. sp. PL VII. , figs. 1 to 9 ; PL IX., fig. 4. 



Colony encrusting, forming a thin sheet 1 millim. to 2 millims. in thickness 

 (Plate VII. , figs. 1 to 3), and over 9 centims. x 7 centims. in greatest extent 

 (Plate IX., fig. 4). 



Ascidiozooids from 6 millims. x 3 millims. on the surface down to 1 millim. in 

 diameter, much flattened from above downwards, so as to form at most slight rounded 

 elevations on the free surface. Ascidiozooids not quite closely placed, leaving some 

 spaces of free test between. Colour (in alcohol) a dull slate-blue, pinkish -red when 

 ulive ; the test nearly white, with a slight pearly lustre. 



Mantle moderately muscular, not pigmented, with well-marked siphons. The atrial 

 siphon has about 20 very delicate tentacles at its base (fig. 7) and there are also some 

 convoluted thread-like outgrowths from the mantle hanging into the peribranchial 

 space. 



Branchial Sac with four well-marked folds on each side, with four to six internal 

 liars on each (PL VII., fig. 4). The dorsal interspace has one bar, close to the first fold, 

 the next interspace has one, the next two have each two bars, and the ventral inter- 

 space has no bar dividing its row of eight or nine stigmata. Most of the meshes 

 contain four or five stigmata each (fig. 4). 



Dorsal Lamina u plain narrow membrane. 





