224 D. J. SCOURFIELD ON EPHIPPIA OF LYNCEID ENTOMOSTRACA. 



A representation of one is given in Fig. 6, and it will be seen 

 that there is a very general resemblance to C. rectirostris in all 

 points, except that the longitudinal markings of the shell become 

 in this species developed into very prominent ridges in the centre 

 of the darkened area, i.e., just over the spot where the egg will 

 be eventually lodged. Each of these ridges can be traced into one 

 of the ordinary shell lines both anteriorly and posteriorly. In front 

 view the projecting ridges can be seen to be somewhat crenulated. 

 In the preserved specimens at my disposal it was impossible to 

 trace out the lines of separation of the ephippium from the rest 

 of the shell, but this does not in the least prove that they do 

 not exist, and I have no doubt that the ephippium of this species 

 very closely resembles that of C. rectirostris in outline and all 

 other characters except the prominent ridges. 



Acroperus harpae Baird. 



Much of what was said about the epliipi3ium of C. rectirostris 

 applies also to this species. There is the same thickening 

 of the chitin at the back (see Fig. 7), the same slightly ragged 

 ventral margin terminating at some distance in front of the 

 posterior ventral angle of the shell, and the shell markings are 

 not perceptibly altered. Of course the general outline differs 

 somewhat from C. rectirostris, being necessarily conditioned by 

 the normal shape of the shell in the species ; but the most notice- 

 able difference in this respect is that the anterior dorsal cusp, 

 which forms such a striking feature of the ephippium of 

 C. rectirostris, is extremely small. The darkening of the 

 shell is not so deep as in Camptocercus, "but on the 

 other hand it spreads nearly uniformly from the back over a 

 large pai-t of the ephippium, instead of being confined to an 

 oval patch just over the egg. The inner membranes around the 

 egg are much more developed than in C. rectirostris, forming, 

 in fact, a quite distinct capsule. That this capsule is really an 

 efficient second line of defence for the egg may be inferred from 

 the fact that, in ephippia which have been moulted for some 

 time, the space between the valves of the ephippium and the 

 capsule may be seen to contain various tiny living organisms 

 such as diatoms, bacteria, etc., while the space within the capsule 

 is quite free from such invaders. The same fact will be brought 

 out in another way when dealing with Chydorus sphaericus. That 



