Mr. C. Spence Bate on Synaxes. 221 



The mandible is strong, and carries a small two-jointed 

 synaphi])od (or appendage). 



All the pereiopoda are simple, terminating in short dactyli. 

 The first pair is the largest, and is tolerably robust ; the fol- 

 lowing gradually decrease in succession until the last, which 

 is more than proportionally smaller than the preceding. The 

 first pair of pleopoda is small and single-branched ; all the 

 others are biramose. The four following slightly diminish 

 in size, the inner branch being biarticulate and slender, the 

 other being uniarticulate and foliaceous. The sixth or poste- 

 rior pair, which forms the outer plates of the rhipidura (tail-fan) , 

 consists of a short basal joint and two foliaceous branches ; 

 and the telson is broad and foliaceous, having more than half 

 its length membranous and flexible. Length about 3 inches. 



Hah. West Indies. 



The carapace is about half tlie length of the animal. 

 It is subcylindrical, being dorsally slightly flattened, so 

 that an angular ridge traverses the sides from the anterior 

 extremity of the outer angle of the orbit to the posterior 

 margin of the carapace. The anterior margin is projected, 

 between the eyes to an acute angle, and outside the same 

 organs to about half the length of the central rostral projec- 

 tion, between which the orbit exists as a deep and more than 

 semicircular excavation, the limits of which are defined by a 

 small inner and outer protuberance. The margin of the orbit 

 is fringed with an even row of small bead-like tubercles, which 

 at the centre is divided by a small crevice or notch. The pos- 

 terior margin is dorsally excavated, being posteriorly produced 

 at the sides and depressed especially laterally, and is edged 

 with a fringe of short hairs, and separated from the rest of the 

 carapace by an even line or fissure. 



The carapace has the surface evenly covered with small 

 granular projections, a prominent few of which form a longi- 

 tudinal line, commencing at the anterior point of the frontal 

 margin between the eyes and terminating near the centre of the 

 stomachal region. Those on the dorsal surface, when closely 

 examined, are connected on the anterior side with three or four 

 small punctures, through which small hairs are presumed to 

 pass, from the circumstance of their being seen to remain on 

 the anterior and lateral portions. 



The pleon is similarly punctated, but more sparingly ; and 

 all the punctures point posteriorly. 



The first somite is scarcely as broad as the carapace, and 

 has on each side a small anteriorly directed aliform process 

 that overlaps the posterior margin and retains the carapace in 

 its position. 



