56 D. J. SCOURFIELD ON THE EPHIPPIUM OF BOSMINA. 



Fig. 6. Upper portion of a lateral band [B. longirostris), showing 

 the loose pieces of chitin at its anterior end, which 

 apparently fall away and produce the slit found in 

 this position in the ephippium, x 280. 



„ 7. Portion of shell sculpture of a specimen of B. longirostris, 

 showing probable early stage in the formation of 

 the line of weakness between the ephippium and 

 the ventral portions of the valves, x 180. 



„ 8. Bosmi/ia lilljehorgi (?), carrying ephippium and winter 

 egg, X 90. 



„ 9. B. lilljehorgi (?), view from above, showing the projecting 

 lateral and dorsal bands of chitin, x 110. 



Note. — The small letters have the same significance throughout, 

 namely : — 



d = Dorsal chitinous band of ephippium. 



j = Junction line between head-shield and valves. This line is actually 



much fainter than represented in the figures. 

 I = Lateral chitinous band of ephippium. 



m = Inner membranes surrounding winter egg. 



s = Slit in valve proceeding from anterior end of lateral band to margin 

 of ephippium. 



w — Line of weakness separating the ventral portion of the valve from 

 the part retained to form the ephippium. The line is doubly-con- 

 toured, but is much fainter than shown in the plate. 



Journ. Quekett Microscopical Chib, Ser. 2, Vol. VIIJ, No. 48, April 1901. 



