Mr. C. Spence Bate on Synaxes. 223 



excepting for a single notch on one side and a corresponding 

 tooth on the opposite, and furnished with a three-jointed 

 synaphipod, the terminal joint of which is covered with nume- 

 rous hairs. 



The posterior oral appendages, as far as I am enabled to 

 determine them without injury to the unique and dried speci- 

 men at my disposal, appear to approximate those of Pah- 

 nurus in the possession of multiarticulate terminations to the 

 outer branches. 



The gnathopoda are flat and broad ; the first pair has the 

 dactylus absent, and generally resembles that of Palinurus. 

 The second has the three terminal joints much narrower than the 

 preceding, the margins of which are thickly furred with hairs. 



The first pair of pereiopoda is stout and strong, the raeros 

 being the widest joint of the whole ; the dactylus sharp- 

 pointed, unguiculate and slightly curved ; the propodos is stout 

 and slightly narrower at the dactyloicl than at the carpal 

 extremity. The carpus is triangular and slightly shorter than 

 the propodos ; the meros is broad and long ; the ischium and 

 basis are short, fused into one triangular joint ; and the coxa 

 is strong and short. The three succeeding pairs of pereiopoda 

 are more slender, but formed on the same type as the preceding, 

 each successively decreasing in proportion ; and the posterior 

 pair is still smaller and more than proportionally slenderer than 

 the others. 



The first pair of pleopoda is subcentrally attached to the 

 somite, and consists of a small, slender, unbranched appen- 

 dage. The second and three following pairs are attached to 

 the inner wall of the coxal plate and are biramose, the inner 

 branch being two-jointed, slender, and cylindrical ; the outer 

 is single and foliaceous. The posterior pairs gradually de- 

 crease in size. The sixth pair of pleopoda is biramose and 

 foliaceous, the anterior portion being hard and calcareous, 

 terminating in small sharp teeth on the outer margin and 

 central ridge, posterior to which the membranous portion is 

 longitudinally ribbed and flexile. 



The telson is broad at the base and rounded at the extremity ; 

 the anterior division is calcareous, and armed with two minute 

 points equilaterally distant from the margins and centre, but 

 the posterior division is membranous and flexile. 



It has been to me a matter of curious interest to observe 

 how in the history of classification every zoologist of note 

 has, previously to the anatomy and development of the sepa- 

 rate genera being well understood, associated the two very 

 dissimilar looking animals of Ihaccus and Palinurus in one 

 family. 



