FOREIGN CORRESPONDENCE. 



149 



calix alone was known, being placed by me and by Mr. Phillips in 

 Poteriocrinus, whereas in reality they belong to another genus, but of 

 which it was impossible then to suspect the existence. 



These are Poteriocrinus granulatus, Phil., P. Calyx, M'Coy., P. 

 Phillipsianus, De Kon., and P. Maccoyanus, De Kon. These species are 

 distinguished, nevertheless, from the true Poteriocrini by the brevity 

 and open form of their calix, which is usually conoid in the others. 

 These latter appear to have smooth stems, formed of articulations, having 

 very nearly the same diameter ; and, in consequence, not possessing 

 the ringed character above referred to. Two of the species which I 

 have to notice have been placed by Mr. M'Coy (Palseoz. Possils inMus. 

 of Cambridge, p. 117), in the genus Cupressocrinus of Goldfussj and I 

 shall not now dwell on the inexplicable error committed by that palaeon- 

 tologist, because I have already had occasion to refer to it in my 

 "Eecherches sur les Crinoides" (p. 88). 



It is almost superfluous to add that the genus in question ought to 

 be placed in the family of Poteriocrinidae. 



Distribution. — All the known species of Hydreionocrinus belong ex- 

 clusively to the Productus-bed" (P. giganteus.) of the carboniferous 

 limestone. Most of the specimens have been found in England or in 

 Scotland — some in the United States. The limestone of Yise has 

 furnished me with two, but one only is special to it. 



{To he continued.) 



FOREIGN COERESPONDEITCE. 

 By De. T. L. Phipson, of Paeis. 



Mercury in tTi& soil of Montpellier — Mud-volcanos of Java — Ancient 

 superstitions — Fearful eruptions — Origin of the mud in these volcanos 

 — Ra/rity of Sulphate of Potash in nature — Abundance of Sulphate of 

 Soda — Beds of this salt in Spain. 



As early as the year 1 760, M. I'Abbe Sauvages made known to the 

 world that mercury, in a metallic state, existed in the soil on which 

 the town of Montpellier is built — a discovery made by himself. Since 

 that time Amoreux, Gouan, Gensanne, and Poitevin have successively 

 mentioned the same fact. Poitevin, in 1830, remarked: We must 



