On the Temperatnre of the Sea, &c. 295 
has ever been found in Europe, it is going too far to consider that as 
a proof of the identity of the beds in which it occurs with our green 
sand. The smooth varieties of it, which are said to resemble the G. 
haliotoidea of Min. Conch. we have not seen; but it probably is that 
species : if so, the consideration of it with Gryphea convexa of Mr. 
Vanuxem and Dr. Morton, (which is G. globosa of Min. Conch, and 
Podopsis grypheoides of the French, and occurs in green sand, as 
well as chalk) Baculites and other shells, will go far to prove what 
those gentlemen have suggested, that the beds in which these shells 
occur are the equivalents of the green sand and chalk formation of 
Europe. 
I will here observe, that although some of the Exogyre of New 
Jersey are ribbed, and others are not, I believe them to be one and 
the same species, inasmuch as the young shells are mostly smooth, 
and specimens are found with every variety of surface, from incipient 
ridges to elevated coste. Another fact, noticed by Mr. Say, is, that 
in old shells the ribs often became indistinct, and even obsolete, It 
seems therefore impossible to derive specific distinctions, in this in- 
stance, from the coste of the Exogyre 5 ; and we must be content.to 
consider all our American specimens as identical until we can sree 
er some less variable characters by which to distinguish them. 
Although the Exogyra costata and E. haliotoidea appear to be 
analogues, they are evidently distinct species; which remark I am 
disposed also to apply to the English Grypheza globosa, and the 
an G. convexa. 
(r he subject will be resumed in the next number of the Jour 
and will there be illustrated with plates —Editor.] 
at 
Arr. IV -—Fragment from Peron, with notices from other voyagers, 
_ On the Temperature of the Sea, at great depths, far from Land. 
Mr. Sillinan—The following is translated from the ‘ Voyage de 
Découvertes Aux Terres Australes,” section 4. Vol. Il. p. 334. It 
seems to me that the facts detailed by M. Péron are inconsistent with 
the theory of M. Cordier, as to central heat, if they do not prove 
Conclusively its entire fallacy. The thermometer used by Péron 
was Reaumur’s, it will be easy to estimate the changes of tempera- 
ture by Fahrenheit, if it is recollected that the zero of Reaumur is’ 
the freezing point or 32° of Fahrenheit, and that four degrees of the 
former are equal to nine of the latter. Yours, 
Steubenville, Ohio, Sept. 20th, 1829. Bens. T coax: 
