98 Mr. T. R. Jones on some species of Leperditia. 



tero-dorsal region, — ^just above and in front of the muscle and 

 central spot*. This last is the position of the eye-tubercles in 

 Leperditia. 



In the LimnadidcE the eyes are quite differently situated. 

 They are closely approximate, and are placed (as in the Daphni- 

 dae) low down on the beaked head (or cephalic rostral buckler) 

 of the animal ; and hence they are sometimes even protruded 

 from between the anterior margins of the valves in Estheria. 



The eye-spots or anterior tubercles of Leperditia^ being near 

 the dorsal edges of its carapace, have an analogous position to 

 that of the eyes on either side of the mesial line of the horizontal 

 carapace in the Apodidce, — or rather, being somewhat further 

 apart (measuring across the hinge-line of the valves), those of 

 CorycceiLS and Caligus. 



Conclusion. — The points of resemblance between the carapace 

 of members of the recent families of Entomostraca and that of 

 Leperditia may be indicated as follows : — 



Limnadid<B. Cypridinince. Apodidce. 

 Resemblance in — 



Outline -}- * - 



Central spot for muscular 1 , i _ 



attachment J 



Vascular markings (sinuses) -{- ■— + 



Vascular markings (ra- \ i — .» 



diating) J 



Situation of the eyes — -f * 



Eye-tubercles — •— 4- 



The above remarks may be of use not only in showing the 

 difficulty that exists in co-ordinating this fossil genus (so far as 

 the remains of the carapace will help us) with its known allies, 

 but also to some extent in illustrating another example '' of the 

 combination in extinct animals of characters separately mani- 

 fested in existing species.^' 



In concluding this notice of the relations of Leperditia, I 

 would observe that the successive changes in the developmental 

 growth of individuals remind us of the gradations of structure 

 observable among allied species ; and, as among the Limnadidce, 

 young individuals t present not a bivalved, but an horizontal 

 carapace, like that of Apus, so the carapace of an Apodoid ideally 

 folded in two along its mesial line, with its two halves drawn 

 together by a transverse muscle, would well represent in most of 

 its important characters the carapace of a Leperditia ; for the 

 eye-spots would be nearly in the relative position required, and 

 the central muscle-spot would be associated with vascular mark- 



* For instance, Cypridina Zealandica. 



t Estheria and Lymnetis, less than a week old : (Joly, Grube). 



