1887.] 



ON CYCLESTHERIA HISLOPI. 



7 



on the middle pairs with a flexible cirrus. Only first pair 

 of legs in male prehensile. Posterior part of trunk in feniale 

 with lamellar, anteriorly curving dorsal processes, setiferous on 

 the edges. Caudal plate short and broad, with two slender mobile 

 claws at the tip. dorsal edge armed with a double row of strong 

 claw-like spines, successively increasing in lengt h to the last 

 pair; two small caudal bristles present above the spines. — 

 Intestine with two simple rounded coeca anteriorly; no distinct 

 liver. Heart elongate, with four pairs of lateral valvular openings. 

 Propagation during the favourable season by means of unfer- 

 tilized summer-eggs, developing directly beneath the dorsal portion 

 of the shell of the parent, as in the Cladocera, the young escaping 

 with the full number of appendages and a well-developed bivalve 

 shell. 



Bemarks. — As may be seen from the above-given diagnosis. 

 the present genus drffers from all other known bivalve Phyllopoda 

 in several very essential points. Thus, the form of the head is 

 rather peculiar. though possibly somewhat more similar to that 

 in Estheria than to that in Limnadia. The complete fusion of the 

 eves into a single organ seems to afford another character not 

 found either in Estheria or in Limnadia; and, moreover, the 

 position of this organ, far remote from the frontal edge. is rather 

 characteristic, and reminds us somewhat of the genus Limnetis. 

 The antennulæ differ from those both in Estheria and Limnadia 

 by their very simple structure, no trace of the lateral lobes oc- 

 curring in both these genera, being present; the antennæ, too, 

 exhibit a peculiar appearance by reason of the strong recurved 

 spines along the upper branch and part of the scape. As to 

 the legs, they are rather inferior in number to those of both Estheria 

 and Limnadia. and their structure exhibits also some well-marked 

 peculiarities. Moreover, only the first pair are prehensile in the 

 male, whereas in Estheria, and also in Limnadia, this is likewise 

 the case with the second pair. Finally, the caudal plate 

 exhibits a most characteristic appearance, from the great develop- 

 ment of the dorsal spines, which are very strong and unguiform 

 whereas in Estheria and Limnadia this is only the case with 



