266 Observations upon Mr. Hailstone's Crustacea. 



Observations upon Mr. Hailstones Crustacea. By J. O. West- 

 wood, Esq. F.L.S. &c. 



I have examined, with considerable interest, the Crustacea 

 forwarded by Mr. Hailstone, captured at Hastings, and beg 

 leave to offer the following observations upon them ; pre- 

 mising, in the first place, in answer to one of his enquiries, 

 that there is no manual containing descriptions of the British 

 Crustacea, Uracil nida, ^4'cari, &c, notwithstanding the evi- 

 dent utility of such a work. 



Of Mr. Hailstone's Crustacea, probably the new Ponto- 

 philus (Jig. 25.) will be regarded as possessing the highest 

 interest, inasmuch as the propriety of the establishment of 

 the group, which was at first confined to a single species, is 

 thereby proved. The character of this genus, as defined by 

 Dr. Leach, separating it from that of Crangon (of which the 

 common edible shrimp [Crangon vulgaris] is the type) con- 

 sisted in the very small size of the second pair of legs, and 

 the length and acuteness of the terminal joint of the external 

 foot-jaws, or pedipalpi. These characters, however, to which 

 that of the spinose shell may be added, have been deemed, 

 by the French crustaceologists, insufficient to warrant the 

 generic separation of the two groups ; and, on considering the 

 characters of the new species from Hastings, the correctness 

 of their opinion must, I think, be admitted ; since it will be 

 seen that, in several respects, its characters are quite inter- 

 mediate between those of the types of Crangon and Ponto- 

 philus. Thus the shell, instead of being armed with a double 

 series of lateral and three rows of dorsal spines, as in the lat- 

 ter, is 3-spinose only, just as in the common shrimp ; while 

 the terminal joint of the foot-jaws is scarcely longer than the 

 penultimate joint, and is broad, flat, and obtuse. The cen- 

 tral piece of the tail is also much longer than in Pontophilus 

 spinosus. Still the minute size of the second pair of legs 

 corresponds with Pontophilus ; whence it will, perhaps, be 

 more advisable to divide the genus Crangon into two sec- 

 tions : first, those with the second and third legs of equal 

 length, the common shrimp ; and, secondly, those with the 

 second legs much shorter than the third, the. Pontophili of 

 Dr. Leach : and, even in the former group, the compara- 

 tively delicate and imperfect structure of the second pair is 

 very evident ; thus proving, in a natural point of view, the 

 generic identity of the two groups. 



Of the two Porcellanas described by Mr. Hailstone, the 

 larger only remained upon the card. It was quite evident 

 that some Z)ermestes had found its way into the box, and 

 devoured not only the specimens of the other species, but 



