Parker. — On the Structure of the Head in Palinurus. 297 



Art. XXI. — On the Structure of the Head in Palinurus, with especial Reference 



to the Classification of the Genus. By T. Jeffery Parker, B.Sc. 



[Read before the Otago Institute, 11th September, 1883.] 



Plate XXV. 



On rny voyage out from England I was much interested to find that the 



marine crayfish [Palinurus lalandii), brought on board at the Cape of Good 



Hope, differed in a remarkable way from the common Enghsh species 



P. vulgaris, in that it had no trace of the stridulating organ, one of the most 



specialized characteristics of this very specialized genus. 



The species of Palinurus are arranged by systematists in two groups or 

 sub-genera, originally founded by Milne-Edwards,* who defines them as 

 follows : — 



" Sous-genre des Langoustes ordinaires. 

 " Les Langoustes ordinaires presentent sur le milien du front une 

 petite dent rostriforme plus ou moins saillante ; l'anneau antennulaire est 

 tres-etroit, de facon que les antennes externes se touchent presqu' a leur 

 base, et recouvrent les antennes internes ; enfin celles-ci se terminent par 

 deux tigelles multi-articulees tres-courtes. 



" Sous-genre des Langoustes longicornes. 

 "Dans cette division naturelle il n'existe sur le bord anterieur de la cara- 

 pace aucun vestige de rostre median ; l'anneau antennulaire est tres-large et 

 presque carre, de maniere a ecarter beaucoup les antennes externes et a 

 laisser a decouvert les antennes internes ; enfin ces derniers organes se 

 terminent par deux tigelles multi-articulees tres-longues." 



The two species mentioned above (P. vulgaris and P. lalandii) as pre- 

 senting such remarkable differences, occur in Milne-Edwards's work as the 

 first and second species of Langoustes ordinaires ; they are also placed to- 

 gether in Heller's tablet as the third and fourth species of the same sub- 

 genus, no hint being given in either work, or in any other at my disposal, 

 of any important morphological differences between them. 



In the present paper I hope to show that a more natural classification 

 of the species of Palinurus may be obtained by taking into consideration 

 certain points in the anatomy of the head, which have hitherto been largely 

 ignored by systematists, although, as it seems to me, of fundamental im- 

 portance. The chief of these have to do with the sound-producing or 

 stridulating organ, first mentioned, I believe, by Leach, J in P. vulgaris, and 

 described at length, in the same species, by Mobius, || and subsequently by 

 myself. § 



* Hist. Nat. des Crustacea, ii., p. 289. \ Malacostraca Podophthalmata Britannia. 

 t Eeise der Novara, Zool. ii., Crustacea, p. 94. || Archiv fur Naturgeschichte, 1867. 

 § Proe. Zool. Soc, 1878, pp. 292 and 442. 



