34 CEYLON PEARL OYSTER REPORT. 



produced into apically setose lobes. Gnathopods without fringes of long plumose 

 seta?. Uropods of male (except in C spinulosa) having only the outer ramus strongly 

 developed. 



Leach having only C latreillii on which to found his genus, availed himself of 

 characters which would exclude many of the forms now grouped under this generic 

 name. The four marks which he used for distinguishing Cilic(ea among the 

 Sphseromidae were : first, the approximate ecmality of the sixth and seventh segments 

 of the perason ; second, the prolonged medio-dorsal process on the anterior division of 

 the pleon ; third, the apical sinus with central lobe in the hinder division of the pleon ; 

 and fourth, the rudimentary character of the inner ramus of the uropods. The second 

 of these characters is conspicuous in fewer than half the species at present assigned to 

 the genus. 



The lobe within the apical sinus of the pleon is found in oidy four of the species, 

 and the fourth character is subject to one curious exception, since in C spinulosa the 

 inner ramus of the uropods is rather longer than the outer. Leach himself evidently 

 suspected that the long process of the pleon might be peculiar to the male, and this 

 has proved to be the case. But the females, so far as is known, besides being without 

 the dorsal process, have the apical sinus, at least usually, simple, and the rami of the 

 uropods subequal. Whitelegge, however, says that " the sexual differences in 

 C. hystrix are very slight," and that in C. stylifera "the female does not differ materially 

 from the male." He thinks it highly probable that the form figured by Haswell as 

 the female of C. hystrix may really be the female of C. spinulosa, Haswell in his text 

 leaving the point ambiguous. Miers regards SpJueroma pubescens, Milne-Edwards, 

 the Cymodocea pubescens of Haswell, as with scarcely any doubt the female of 

 C. latreillii. H. F. Moore explains Cymodocea bermudcnsis, Ives, as female of 

 C caudata (Say), and suggests that Dynamene nodidosa, Richardson, is the female 

 of C. caudata- gil liana, Richardson, nodulosa being apparently named by a slip of 

 the pen instead of tuberculosa. But S. J. Holmes makes it fairly certain that 

 Dynamene tuberculosa is the female of Ciliccea cordata, Richardson. As tuberculosa 

 has page precedence, it will supersede cordata, and not without advantage to the 

 genus, since to many ears cordata and caudata are indistinguishable. The confusion 

 caused by the sexual dimorphism in this genus will not, perhaps, be very easily 

 disentangled. 



The following synoptic view of the species rather suggests that, for practical 

 convenience, those which are devoid of the great dorsal process might be grouped 

 under a sejmrate generic name : 



Anterior division of pleon in male with 



long medio-dorsal process 2. 

 Anterior division of pleon in male 



without such process 11. 



