10 



convex or alrrrost parallel. A distinct carina runs along the 

 middle of the dorsal surface from the rostrum, marked by a single 

 or double spine, to the posterior margin, which is concave. 

 On the part of the carapace below the lateral margin there are 

 two less distinct carinae, one running to the base of the antennae., 

 and the other to the base of the chelipeds ; both start from near 

 the postero-lateral angle af the carapace. These three carinae 

 all bear more or less well developed spines which are of great 

 importance as specific characters. There is also usually a 

 row of spines on the outer cardiac area running parallel to the 

 posterior part of the lateral margin. The front edge of the 

 carapace is excavated on either side into a deep sinus in which 

 lies the fixed eyestalk. 



The abdomen tapers rapidly to the telson, which always ends 

 in a long narrow point. The abdominal terga bear median 

 crests, which are sometimes developed into huge forward- 

 curving spines. The pleura of the second segment are much 

 larger than those of the other segments. 



The eyestalks fill the sinuses in which they lie, and are opaque 

 and dull except for a small circular area which is present at the 

 posterior dorsal end in some species ; this part is translucent 

 and soft. The anterior end of the eyestalk, which may or may 

 not bear a small spine, gives off a branch which passes outwards 

 and downwards beneath the ant ero -lateral angle of the cara 

 pace ; its tip is translucent like the dorsal area already men- 

 tion. 



The basal joint of the antennular peduncle is produced into 

 an elongated and pointed scale on the inner side, and bears one 

 or two spines at its outer angle. There is a narrow antennal 

 scale. The outer antennulary flagellum is always very short 

 and slender, the inner one nearly equal in length to the antenna, 

 which is usually slightly longer than the carapace. The renal 

 tubercle is very well developed and presses against the base of 

 the antennulary peduncle, in which there is a rounded hollow 

 for its reception. 



The oral appendages are very uniform in the different species 

 and are described in detail later. 



All five pairs of thoracic legs are chelate in the female ; in 

 the male the last pair is more or less imperfectly chelate. The 

 first pair is very long, often longer than carapace and abdomen, 

 and the joints are all more or less flattened. The fingers are 

 long and slender with strongly curved tips which cross when 

 closed. The other pairs of legs become successively shorter 

 and feebler backwards. 



The pleopods are long and slender with a rod-like appendix 

 interna. There is no transverse suture on the uropods. 



There is no epipodite on the second maxillipedes ; that on 

 the third maxillipedes may be a mere papilla or of fair size. 

 Epipodites and podobranchs are present on the first four pairs 

 of thoracic legs and vary in size, sometimes reaching far up into 

 the branchial chamber, sometimes hardly ascending into the 



