THE GENUS SARON 391 



though it is impossible to identify them, and it may well be that Latreiites is among the 

 forms from the Red Sea. 



In view of the doubtful relations between the various genera of the Hippolytidae 

 further study of this well-defined group of larval forms would be useful, and the problem 

 of their identity would be easily solved at Ghardaqa if it could be attacked at a rather 

 later season than that of my own visit, and with better opportunities for getting 

 plankton. 



Saron marmoratus (Olivier) 



Stage I. Length 2-5 mm. (Figs. 106-112). 



Carapace with small pterygostomial spine and two anterior marginal teeth; anterior 

 and posterior papillae present, small; ventral margin sinuate, with small tooth at 

 posterior angle; rostrum absent. Pleura of abdominal somite 2 pointed, the rest 

 rounded ; without dorsal or dorso-lateral spines. Telson rather narrow, with 7+7 spines. 



Exopod of antennule with inner feathered seta long, and four aesthetes, of which one 

 is slender and pointed, with a narrow hyaline margin. Antennal scale short and broad, 

 with two outer setae and ten inner and terminal setae ; four terminal segments distinct ; 

 endopod spine-like. Maxillule without outer seta on basis ; endopod unsegmented, with 

 five setae. Endopod of maxilla segmented, with basal lobe very well marked ; lacinia 2 

 large; exopod with five setae. 



Exopods of maxillipedes 2 and 3 with six setae, the four apical setae symmetrically 

 placed. 



Rudiments of legs i and 2 biramous. 



General colour very red, with many deeply placed red chromatophores. When these 

 are contracted a pale yellow tinge remains general. 



As I supposed at the time that the Saron larvae were hatched that the larvae found in 

 the plankton belonged to the same species, no attempt was made to keep the larvae 

 through a moult. I find it now impossible to be sure which, if any, free larvae belong to 

 Saron. There is a species which has the pleura of the abdomen of the shape characteristic 

 of S. marmoratus, but there is also another form of stage I which is like Saron, but has a 

 small downturned rostrum, which Saron has not. There are therefore apparently three 

 species. One which is described below is quite distinct by reason of its large rostrum 

 and the shape of the abdominal pleura, but the others cannot be satisfactorily dealt with. 

 One specimen in the last stage moulted to post-larval and should have given the 

 opportunity of identifying its genus, but this specimen was lost by accident before the 

 essential characters had been made out. I give, therefore, only a description of a stage II 

 larva which I believe to be Saron, and leave the rest undescribed. 



Stage II. Length 3-3 mm. 



Rostrum shorter than antennule, triangular in dorsal view, and very slender in side 

 view. Carapace without supra-orbital spine ; with large pterygostomial spine and an 

 anterior process extending under the eye. Abdominal somite 2 with pleura large and 

 pointed, the rest rounded. 



