1866.] WOODWARD OLDEST BRITISH CRAB. 493 



of the country at the present day, frost and rain appear to play the 

 most important part in the higher mountains of the granitic district; 

 but the chemical action of the atmosphere seems to affect to a greater 

 degree the sandstone, by destroying the ferruginous cement which 

 binds together its particles, and thus decomposing it. Yet the 

 changes that are taking place are apparently so gradual and slow, 

 that I feel convinced that the peninsula of Sinai is to this day but 

 little altered in its nature from what it was when the children of 

 Israel wandered in its wilderness more than 3500 years ago. 



2. On the oldest known British Crab (Palseinachus longipes) from 

 the Forest Marble, Malmesbury, Wilts. By Henry Wood- 

 ward, Esq., F.G.S., F.Z.S. (of the British Museum). 



[Plate XXIV. fig. 1.] 



I AM indebted to my friend Professor Thomas Bell, F.E.S., of the 

 Wakes, Selborne, Hants, for the opportunity of describing this new 

 and beautiful crustacean. 



The specimen is from the Forest Marble of Malmesbury, and was 

 discovered several years ago by the well-known collector of Oxford- 

 Clay and Oolitic fossils, Mr. Wm. Buy. It will be seen to have nearly 

 all its limbs in situ ; and it shows the carapace with four segments of 

 the abdomen united to it, resting upon a slab of Forest Marble covered 

 with the remains of Pentacrini, Acrosalenia hemicidaroides, shells of 

 Avicula, JRhynchonella, and traces of the drift-wood to which the 

 OoHtic Pentacrinites (like the barnacles of our modern seas) were 

 attached. 



The limbs of this crustacean are extremely long and slen- 

 der; and in this respect, and also in their form and in that of 

 the carapace, with its remarkable prominent tubercles in front, it 

 closely resembles the common " Spider Crabs " (the Maiadce and 

 Leptopodidce) living on our own coasts at the present day, and the 

 Great Japanese Crab, the Inachus Kmnpferi, of De Haan. The Upper 

 White Jura of Germany has yielded carapaces of several minute 

 Crustacea, which are either Brachyurous or Anomurous ; but as no 

 limbs or abdominal segments have been met with, it is more doubt- 

 ful where to place them in a classification of the fossil forms. 



Professor Eeuss* and H. von Meyer f have described three genera 

 and twenty -five species of these forms (some of which have been re- 

 produced iu Mr. Lowry's ' Chart of Fossil Crustacea '$) ; but none of 

 them are comparable with the carapace of Palceinachus. 



* Sitzungsb. K. Akad. d. Wiss. in Wien, xxxi., 1858. 



t Paleeontogr. Cassel, 1859-61, Bd. vii. p. 183, t. 23 (Monograph on the 



I Falainachus lonffipes is there figured with the generic name Protocarcinus 

 which had been given to it (in MS.) by Prof. Bell; but it is not adopted here, 

 first, because the fossil has no affinity to Carcinus, and secondly, because the 

 prefix " Proto^^ is objectionable in Palaeontology. 



