GENERIC CHARACTERS OF HIPPOLYTIDAE 399 



Antennal scale narrowing towards end, with large apical spine ; endopod short and 

 stout. Maxilla, exopod very broad in front, with very large proximal seta. 



Maxillipede i coxa large; epipod large; exopod with five setae. Maxillipede 3 with 

 ten setae on exopod. 



Leg I endopod short, not distinctly segmented, with incipient chela; exopod with ten 

 setae. Leg 2 endopod rudimentary, bifid at end. Legs 3-5 rudimentary. No rudiments 

 of exopods seen on legs 2-5. Four large rudiments of pleurobranchs on legs 1-4 and very 

 small one on leg 5 ; no epipods. 



Pleopods present as small buds. Uropods with numerous setae on both branches. 



One specimen of this form was found in plankton from Barrier Reef St. i . A young 

 specimen, perhaps in post-larval stage 2, St. 65 is recognizable as belonging to 

 L. miicronaUis. The larva almost certainly belongs to the genus Latretites, and it is a 

 fair speculation to refer it a species which was also taken in plankton in much the same 

 locality. 



DISCUSSION AND SUMMARY OF GENERIC CHARACTERS 



The general characters of the Hippolytid larvae then known were summarized by 

 Miss Lebour (1932), and I give an extended summary below. It must be confessed that 

 they do not throw any clear light upon the systematic grouping of the Hippolytidae, 

 though they suggest that the separation of a Latreutid group is not justified. As Miss 

 Lebour has said, the characters of the larvae point to a division into new families or 

 subfamilies, but our knowledge is not sufficiently complete to carry the suggestion 

 farther. It is peculiarly disappointing that I am unable to determine the parentage of the 

 remarkable group of larvae from the Red Sea, since the characters of Saroti and 

 Latreutes are left uncertain. Before any definite conclusions can be put forward it is 

 necessary not only to know more about these two genera, but also the development of 

 Thor, which, on adult structure, seems to be inseparable from Spirontocaris (Lebour, 

 1936)- 



The larval characters of the Hippolytidae, so far as they are known, may be sum- 

 marized thus: 



Hippolyte 



Rostrum present in stage I, remaining simple, broad at base. 



Carapace without supra-orbital spines, or with very small spines in late stages ; margin 

 denticulate. 



Abdominal somite 5 with dorso-lateral spines. 



Telson broad in early stages, and later with two pairs of lateral spines and twelve 

 terminal. 



Anal spine present in late stages. 



Antennal scale with tendency to lose segmentation; endopod spine-like in stages I 

 and II. 



