BELONGING TO BAPHNIA AND OTHER ALLIED GENEBA. 243 



rounded off behind : dorsal margin of the valves very gently 

 arched towards the front, but almost straight for the greater part 

 of its course, ventral forming a continuous gentle curve ; ante- 

 rior and posterior extremities nearly equal, broad and obliquely 

 subtruncate ; the spine is on a line with the dorsal margin and 

 directed slightly upwards. Antennules (fig. 9) composed of a 

 peduncle bearing a single long seta which is indistinctly divided 

 into three tracts, the middle portion very slender, the apical 

 portion slightly bulbous at its base and thickly beset with very 

 minute hairs. The peduncle has near its apex a rosette of nine 

 papillae, supplied with nerve fibres and giving origin as usual in 

 Daphnice to delicate sensory filaments. Post-abdominal laminae 

 (fig. 6) bearing a wide spinule-fringed finger-like lobe just in 

 front of the terminal unguis, and in front of the lobe a deep 

 sinuation, which is fringed with about twelve curved spines : the 

 dorsal abdominal processes are quite rudimentary. The margins 

 of the shell are spiniferous behind the middle as in the female, 

 and the ventral margin bears also a dense fringe of hairs which 

 are thickest and most numerous about the anterior angle just 

 behind the head. Length, 2 mm. 



This is the largest and at the same time one of the less com- 

 mon species of Daphniada,, though generally distributed over 

 Europe, "Western Asia and North Africa. It has not been found 

 in America, nor is there any record of its occurrence in Scotland 

 or Ireland. In England it has been recorded by Dr. Baird from 

 Bexley Heath, Kent, and Norwood Green, Middlesex. Dr. Nor- 

 man has found it at Layton Farm, near Sedgefield, co. Durham, 

 and I have myself taken it in a pond at Canal Farm, High 

 Barnes, near Sunderland, in a quarry pond between Plessey and 

 Blagdon, Northumberland, and at Tresco (Scilly Islands). Mr. 

 Scourfield records that in 1893 this species " occurred in aston- 

 ishing abundance in the London Docks." 



The development of the male of D. magna well illustrates one 

 of the difficulties which beset the naturalist in the investigation 

 of species whose life-history is not thoroughly known. In my 

 gathering from the Plessey pond all the males which I could 

 find presented characters of antennules and caudal lamellae quite 



