230 D, J. SCOURFIELD ON EPHIPPIA OF LYNCEID ENTOMOSTRACA. 



whole of the dorsal half of the shell, and the chitin at the back is 

 much thickened. The surface of the shell is everywhere covered 

 with extremely closely-set striae similar to what is found in 

 Alona affinis and Leydigia acanthocercoides, and these fine lines are 

 not modified in any way in the ephippial females. In passing it 

 may be pointed out that, although Professor Sars does not mention 

 these fine striae in his description of the species (6), they un- 

 doubtedly exist, but can only be properly seen with the most 

 careful illumination, and high magnification. Under these 

 conditions they can be resolved into rows of tiny dots (black or 

 white accorcUng to the focus), almost comparable in delicacy to 

 diatom markings. There is no other shell sculpture. I was able 

 in this instance, even with the preserved specimens at my 

 disposal, to demonstrate a line of weakness running obliquely 

 across the shell striae in the direction of the ventral margin, but 

 I could not make out its real nature quite satisfactorily. In one 

 or two places, however, distinct cells or pieces of chitin could be 

 seen, and upon these there were no striae. The ephippium when 

 moulted would most probably be very similar in outline to that 

 of Alona costata, and in confirmation of this Professor Sars notes 

 that the single egg becomes covered with a ^;m'^ of the moulted 

 carapace. In the central and darkest part of the shell there is a 

 fairly evident reticulated structure consisting of hexagonal cells 

 of rather large size, apparently containing masses of fibrous 

 material. These are probably connected with some special 

 development of the inner layer of the carapace, such as we 

 have seen to take place in other cases. ' 



Leydigia acanthocercoides (Fischer). 



A detailed description of the ephippium of this species has been 

 given in a special paper (10), and it will therefore be sufiicient 

 for our present purpose if the main features only are referred to. 

 Side and front views are given in Figs. 18 and 19, and from these 

 it will be seen that it is provided with two enormous hooklike 

 processes which are evidently the darkened, and possibly thickened, 

 margins of the original shell. So far as known at present, this is 

 a feature that is unique among Lynceid or any other ephippia, 

 the nearest approach to such an arrangement being found in 

 Daphnia magna (for a few remarks on which species see the 

 paper just referred to). The portion of the original shell forming 



