76 THE VOYAGE OF H.M.S. CHALLENGER. 



b. The first antennal somite armed with four teeth. 



a. Four conical teeth remote. 



a Teeth tolerably large, equidistant, and forming 

 a quadrangle. 



* Carapace spinose all over — Palinurus 

 spinosus, Edw. ; Palinurus americanus, 

 Edw. 



** Carapace spinose anteriorly, tuberculated 

 posteriorly — Palin urus interruptus, 

 Randal. 



b Teeth minute, scarcely approximate on the 

 median line, anterior and posterior much more 

 distant — Palinurus argus, Latr. 



/3. Four conical teeth approximated and connected at the 

 base — Palinurus ehrenbergi, Heller ; Palinurus penicil- 

 latus, Olivier. 



c. First antennal somite armed with eight teeth — Palinurus dasypus, 



Fabr. ; Palinurus burgeri, De Haan. 



In the classification of the several genera which belong to this family the three 

 authors, Edwards, Gray, and Heller have made the two great divisions dependent 

 chiefly upon the one having a central rostrum to the frontal margin of the carapace, 

 and the flagella of the first pair of antennas short, while in the second there is no central 

 rostrum and the flagella are long. 



However, there appears to me to be a great natural distinction between the form 

 known as Palinimis lalandii, Lam., in which the frontal rostrum is so far advanced and 

 depressed as to unite it with the upper surface of the somite of the second pair of 

 antennas, thus enclosing the ophthalmic somite within an orbital chamber, instead of 

 leaving it exposed as in Palinurus vulgaris, in which the rostrum is reduced to a short 

 pointed process. This also appears to me to be the case in Heller's species of Palinurus 

 hugelii, but since Heller has not mentioned it in his description, nor shown it in his figure, 

 I am precluded from asserting this with confidence. 



It appears therefore that Palinurus lalandii should form a separate genus (Palinostus) 

 gradually leading to Synaxes, and so on to the family of Astaeidse, according to the 

 arrangement here followed and indicated on p. 56. 



