Abstracts of Foreign Memoirs. 265 
Crinoideenreste’ (A contribution to the knowledge of the fossil state 
of Crinoid-remains), by Herr A. W. Stelzner. With one Plate. This 
paper is a contribution to our knowledge of the microscopic structure 
of Crinoidal remains, and of the causes which produce the peculiar 
crystallization that has for so long been known to characterize 
Echinoderms. The author first gives a critical notice of the various 
essays on the subject, which have appeared since that of Hessel* in 
1826, and then describes in detail the appearances under the micro- 
scope presented by prepared longitudinal and transverse sections of 
the stems and arms of several species of Crinoids. The conclusion to 
which the author arrives is identical with that enunciated by Dr. 
Carpenter in ‘The Microscope and its Revelations’ (p. 345), and 
quoted in a postscript by Herr Stelzner, who, it appears, was not 
aware that so much had been done in this direction until after his 
paper was written; this conclusion may be thus stated: In the 
cylindrical stems of Encrinites the calcareous network is uniform 
throughout, or very nearly so; but in the five-sided Pentacrinites a 
determinate pattern is formed, through a difference of texture in 
various parts of the cross-section, and these patterns, although always 
belonging to one general type, are nevertheless sufficiently different 
to be recognized apart on an examination of the transverse sections 
of different stem-joints. 
6. ‘Ueber die Entstehung des Travertins in den Wasserfillen von 
Tivoli’ (On the Origin of the Travertin in the Cascades of Tivoli), 
by Dr. Ferdinand Cohn. The Travertin of the neighbourhood of 
Tivoli comprises four varieties, and in this paper the author discusses 
at length the origin of two of them, namely, the ‘ Shaly Travertin,’ 
and the ‘Confetto,’ giving merely a sketch of the characters of the 
other two—the ‘Thick Travertin’ or the Travertin of architecture, 
and the so-called ‘ Alabaster’ of the Roman artists. 
The ‘shaly’ variety consists of a succession of beds of more or less 
earthy carbonate of lime, and composed of a great number of cylin- 
ders of travertin, each of which has been formed in concentric layers 
round a vegetable nucleus. The author is of opinion that the plants 
are the primary cause of the deposition of the carbonate of lime, but 
that the subsequent stages in the formation of the deposit are 
altogether unconnected with organic laws. In support of this opinion 
he observes that, if the cause of the deposition of carbonate of lime 
were merely the exposure of the water to the atmosphere, the deposit 
would first appear upon the surface as a film,—which is not the fact 
in this case, although it is so at the thermal springs of Karlsbad, &c. 
Respecting the second variety of Travertin, Dr. Cohn strives to 
show that its deposition is not owing to the sulphurous acid which 
emanates from the Solfatara of Tivoli, in which it is formed, as on 
analysis he found it to contain no sulphides, but only carbonates. 
H. M. J. 
* Einfluss des organischen Kérpers auf den unorganischen, nachgewiesen an 
Enkriniten, Pentakriniten und anderen Thierversteinerungen, Marburg, 1826, 
VOL. I.—NO. VI. T 
