MKPUS.K. 141 



The sensory vesicles have one otolith, but occasionally a vesicle was seen with two 

 otoliths, which may have been caused by twinning. 



(a) Umbrella about 5 millims. in diameter. About 28 tentacles. 

 ('') " 7 ,, 36 



(<0 15 72 



Irene palkensis, n. sp. Plate III., figs. 12 to 16. 



Description. Umbrella watchglass-shaped, about four times as broad as high. 

 Velum narrow. Stomach short, situated upon a long cylindrical peduncle. Mouth 

 with four short lips, which have a folded margin. Four radial canals. Gonads linear, 

 extending from the base of the peduncle to near the margin of the umbrella. Tentacles 

 about 50. Usually two or three marginal bulbs between every two tentacles. 

 Excretory pores opposite the basal bulbs of the tentacles and all the marginal bulbs. 

 Sensory vesicles about 2 to 4 between every two tentacles, each vesicle with two 

 otoliths (variation 1 to 4). 



Size : Umbrella up to 20 millims. in diameter. 



Locality : Palk Bay, north of Ceylon, five specimens on March 1G. 

 Notes. The five specimens are all in a damaged condition, especially as to the 

 gonads and the margin of the umbrella. The smallest is about 1 5 millims. in diameter 

 and the largest about 20 millims. The gonads are upon the sub-umbrella along the 

 radial canals. One specimen has the gonads extending from near the margin of the 

 umbrella up to the peduncle, and for a short distance down the peduncle. The 

 number of tentacles is only given from an estimation, as not one specimen has even a 

 quadrant of the margin of the umbrella in a perfect condition. The basal bulb of the 

 tentacle is somewhat globular when the tentacle is contracted, and more cone-shaped 

 and tapering when the tentacle is expanded. On the inner side of the basal bulb 

 just above the velum there projects an excretory pore. These pores are conspicuous 

 and clearly visible when expanded, but almost invisible when contracted. Cirri were 

 specially searched for, but none were seen. The marginal bulbs are small, and to 

 judge from their appearance in one of the specimens, I think that some are capable of 

 developing tentacles. Their number between every two tentacles is variable, usually 

 two or three, sometimes only one. All these bulbs have excretory pores, similar to 

 the pores opposite the basal bulbs of the tentacles. The sense-organs are closed 

 vesicles with generally two otoliths (rig. 14), occasionally three to four otoliths, rarely 

 one. The otoliths possess well-marked eccentric zones, which are conspicuous in 

 specimens which have been apparently killed with a re-agent containing osmic acid. 



At first sight Irene palkensis and Irene ceylonensis look very much alike, but after 

 an examination of the organs on the margin of the umbrella I came to the conclusion 

 that they were distinct species. Irene ceylonensis has about twice as many tentacles 

 without a series of marginal bulbs in between them, and there is a difference in the 

 shape of the basal bulbs of the tentacles, but I attach more importance to the sense- 



