Parxer.—On the Structure of the Head in Palinurus. 297 
Arr. XXI.—On the Structure of the Head in Palinurus, with especial Reference 
to the Classification of the Genus. By T. Jerrery PARKER, B.Sc. 
[Read before the Otago Institute, 11th September, 1883.] 
Plate XX 
On my 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 English 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 présentent sur le milien du front une 
petite dent rostriforme plus ou moins saillante; l'anneau antennulaire est 
trés-étroit, de fagon que les antennes externes se touchent presqu' à leur 
base, et recouvrent les antennes internes; enfin celles-ci se terminent par 
deux tigelles multi-articulées trés-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 médian; l'anneau antennulaire est trés-large et 
presque carré, de maniére à écarter beaucoup les antennes externes et à 
laisser à découvert les antennes internes ; enfin ces derniers organes se 
terminent par deux tigelles multi-articulées trés-longues.”’ 
The two species mentioned above (P. vulgaris and P. lalandit) 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 table} 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,{ in P. vulgaris, and 
described at length, in the same species, by Móbius,|| and subsequently by 
myself. $ 
* Hist. Nat. des Crustacés, ii., p. 289. | Malacostraca Podophthalmata Britannia. 
+ Reise der Novara, Zool. ii., Crustacea, p. 94. || Archiv fiir Naturgeschichte, 1867. 
$ Proc. Zool. Soc., 1878, pp. 292 and 442, . 
