226 Mr. C. Spence Bate on Synaxes. 



The eyes are those of the Scyllaridas ; the second pair of 

 antennae are tliose of the Palinuridge. The legs are common 

 to both forms, and the carapace belongs to neither. The frontal 

 region resembles neither ; and the posterior resembles both, as 

 also does the pleon, whereas the pleopoda are modelled on 

 the type of those of the Scyllarida, and the tail-fan is that of 

 both. 



The first thing that strikes the observation is the rostri- 

 form advancement of the frontal margin, as being very diffe- 

 rent from that of either Scj/Uarus or Palinurus. In Panidirus 

 the frontal margin in the median line does not advance 

 beyond that of the eyes ; but in Palinurus marinus there is a 

 small triangular prominence that projects above the ophthal- 

 mic somite in the median line. In Palinurus Lalandii this 

 prominence is still further produced, and is so far advanced 

 that it reaches beyond the ophthalmic somite, which it covers, 

 and, dipping down, meets the inner portion of the ventral 

 surface of the third somite, and so forms an imperfect orbit *. 

 In Synaxes the rostral prominence is so far advanced that it 

 reaches to the extremity of the third or first free joint of the 

 second pair of antennae, beneath which the anterior and inner 

 angle of the second joint of the second pair of antennae is 

 visible, and is seen to articulate with the inner and posterior 

 angle of the next joint. 



Laterally, on the outside of the orbit, the frontal margin is 

 produced considerably in advance of the line of the organs of 

 vision, and is longitudinally folded at an obtuse angle beneath 

 the ventral surface. This antero-lateral development of the 

 carapace (which I do not remember to exist anywhere so pro- 

 minently, except in Polycheles and its generic allies) produces 

 in the frontal margin of the carapace an orbit that is almost as 

 deep as that of Scyllarus. The posterior margin of the cara- 

 pace is not free as in the Astacidag, but firmly secured in its 

 position by an osseous tubercle {pereiocleis) attached to the last 

 somite of the pereion, and lodged in a corresponding closely- 

 fitting hollow on the underside of the carapace, so that it cannot 

 be raised as we see that some Crustacea have the power of 

 doing. The anterior somite of the pleon overlaps laterally, by 

 means of small wing-like processes {pleocleis), the posterior 

 margin of the carapace. This is a feature strongly pronounced 

 in the Scyllaridas and in Polycheles and its allies; it also 

 exists to some extent in the Palinuridge, but to a less efficient 

 degree. 



The ventral surface of the pereion in our female specimen 



* I am much inclined to think that P. Lalandii of Edwards must gene- 

 rically be separated from both Pamdirus and Palinurus. 



