704 



Proceedings of the Royal Irish Academy. 



Dipurena halterata (Forbes). 



Slahleria halterata, Forbes, 1848, p. 53, pi. vi. 

 Slalheria eatenata, Forbes and Goodsir, 1851, p. 311, pi. x. 

 Dipurena halterata, Haeckel, 1879 ; Browne, 1897, P. Z. S., p. 816^ 

 pi. xlix. 



This is a scarce Medusa at Valencia, but it has not often been 

 recorded from other localities, though its distribution extends 

 from Mull to Jersey. 



In 1895, taken once in April, July, and September. 



In 1896, once in July and September. 



In 1897, once in August and September. 



In 1898, once in April, twice in June, once in July and 

 November. 



Solitary specimens were usually taken; but on July 21st, 

 1898, the Misses Delap had the good fortune to capture four- 

 teen adults, and kindly sent them to me for examination. The 

 umbrella of the smallest measured 5 mm. in length and width, 

 and that of the largest 8 mm. in length and 6^ mm. in width. 

 This Medusa is remarkable for having very large clusters of ne- 

 matocysts, forming conspicuous rings at the ends of the four 

 tentacles. By these rings the species may be easily distinguished 

 from D. ophiogaster. The number of rings of nematocysts upon 

 the tentacles of the specimens taken in July varies fi'om one to 

 five, as the following list shows : — 



Umbrella-length, 

 inm. 



Number of rings on each 

 of the four tentacles. 



Remarks. 



5. 



1, 2, 2, 3. 





5. 



2, 2, 2, 2. 



The large terminal bullet- 



5. 



4, 4, 4, 4. 



shaped cluster of nema- 



6. 



3, 3, 3, 3. 



tocysts is not coimted in 



7. 



3, 4, 3, 5. 



with rings. 



8. 



1, 3, 3, 4. 





In the earliest stage, about 1 mm. in length, there is only a 

 terminal cluster of nematocysts ; the rings appear later, and the 

 uppermost one of the series is the youngest. 



