86 
CRUSTACEA. 
Section LOCTJSTiE, Latr. 
Genus SCYLLARUS, Latr. 
16 . SCYLLARUS ANTARCTICUS.* Fair., Suppl. Entom. p. 399 . sp. 3 . Fig. Seba, 
Mus. 3 . tab. 20 . fig. 1 . — Herbst., taf. 30 . fig. 2 ; Cancer ( Astacus ) ursus 
major. 
In Latreille’s arrangement of the Genus Scyllarus, ( Nouv . Diet. d’Hist. Nat. t. 30. p. 450,) this 
species would rank under a division intermediate to the two there proposed, which might be thus 
characterized : 
II. Oculi ex clypei angulis mediaque parte cequidistantes ; articuli pedipalporum externorum secundi neque crista, 
neque sulcis transversis instructi. 
A. lamina Crustacea ex f route prodeuns. 
The figure in Seba represents more accurately than that of Herbst the small triangular crusta- 
ceous lamina projecting from the middle of the anterior margin of the carapace, and also the dispo- 
sition of the larger tubercles along the middle line of the carapace. In Herbst’s figure, probably 
taken from a dried specimen, the middle lamina of the tail is represented too short ; it should extend 
as far as the lateral laminae. As the description of the latter carcinologist is limited to the forms 
and colouring of the carapace, and that of Fabricius to the specific formula, it becomes necessary to 
add that the first two joints of the external foot-palpe are trihedral, compressed, with their inner 
margins slightly dentated ; the second joint having neither an outer dentated crest, nor transverse 
furrows, as in the Ibacus Peronii of Dr. Leach ; from which species this specimen also differs, in 
having more numerous dentations (eight) along the front border of the peduncle of the external 
antennae; and in having a less deep incisure at the sides of the carapace, extending only one-third of 
the way towards the middle line. Whilst, however, it differs in these particulars, in general aspect 
it closely resembles the before-mentioned species, and forms the connecting link between it and the 
species which have their eyes situated at the angles of the shell ; for which reason, in addition to the 
objections urged by Latreille in the work above quoted, and in the Encyclopedic Methodique, (Art. 
Scyllarides,) the generic character proposed by Dr. Leach for Scyllarus incisus, Latr., appears not to be 
founded in nature. This specimen of Scyllarus has its stomach inverted. It was taken at Carysfort 
Island, and is called by the natives XJla papapa. 
* In this species the first or cephalic ganglion is situated beneath the middle of the frontal margin ; it is smaller in 
proportion than in other macrourous Crustacea, e. g. Astacus and Palinurus ; it gives off a pair of nerves to the mesial 
antennae, and a large pair which pass directly outwards to the eyes ; the connecting chords diverge, pass down on either 
side the stomach, and approximate below, to join a large ganglion which is situated on the same transverse line as the 
deep lateral incisures of the carapace. From this ganglion nerves proceed to the palpi and instrumenta cibaria, and a 
large pair also passes outwards, gives off a branch to the muscles of the eye-stalk, and winds round the crustaceous sep- 
tum that divides the branchiae from the abdomen ; it then proceeds downwards, and is distributed exclusively to the 
branchiae. 
After leaving this, which might be called the respiratory ganglion, the connecting chords diverge a little, and four 
ganglions are formed upon each chord before they again unite ; these supply the first four pairs of legs, whilst the fifth 
derives its nerves from the ganglion formed at the junction of the chords. This divergence of the lateral chords may be 
observed in Astacus and Crangon, but in a less degree than in Scyllarus ; it is most remarkable in the Brachyuri, the 
interspace being almost a complete circle in Cancer Pagurus. The degree of divergence has an evident dependence on 
the space which exists between the origins of the corresponding claws on each side. Six ganglions are situated on the 
remainder of the chords, which continue in apposition as far as the tail, where the last ganglion gives off three pairs of 
nerves, the two lateral supplying the lateral laminae of the tail, the middle pair passing on either side the termination of 
the intestine, to end in the middle lamina. 
