470 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Thirty-five species of Echinodermata have been 

 recorded from the conventional area of the Irish Sea 

 known as the L.M.B.C. District, and all are fonnd in the 

 immediate neighbourhood of the Isle of Man. The larvae 

 of three species, viz., Henricia sanguinolenta, Asterina 

 gibbosa and Amphiura elegans are non-pelagic, while 

 that of a fourth, Antedon bifida, is pelagic for only a 

 brief period. In the present paper only the pelagic forms 

 come under notice; and of these, twelve can with 

 certainty be referred to their respective species. 



The occurrence of Echinoderm larvae in nearly all 

 the months of the year has been observed; but, so far as 

 my own experience goes, the largest number of 

 individuals appear in the latter half of February, July, 

 early August, and the greater part of September. These 

 records refer particularly to the years 1907 and 1908, 

 when a large proportion of the specimens upon which 

 this memoir is based were collected. Most of the same 

 species were observed in the years 1909 and 1910, but in 

 remarkably diminished numbers. The records of Scott 

 (14) show that in the year 1906 Echinoderm larvae were 

 present in the plankton of Port Erin Bay in March and 

 September, but these records are probably incomplete. 

 In September, 1911, 1912, and 1913, several species 

 observed in July in previous years appeared in 

 diminished numbers. In March and April, 1914, one 

 spatangoid pluteus was abundant, while one ophiopluteus 

 and two Asterid larvae were not uncommon at the end 

 of March and in April. 



Larvae of Asteroidea. 



Considering the fact that twelve species of Asteroidea 

 are found in the immediate neighbourhood of Port Erin, 

 and that the larvae of at least eight of them are known 



