236 



/. M. Safford on the Genus Tetradium. 



I have thus taken the liberty of offering to your Lordship, a& 

 the Member of Her Majesty's Government under whom I serve, 

 my view upon a subject of which I have long thought; and 

 have only now to request that, in giving it your best attention, 

 you will submit this letter to Her Majesty's Government, and 

 particularly to the consideration of the Minister who may be des- 

 tined to be charged with the education of the country. 



Geological Surrey Office, Jermyn Street, Jan. 25, 1856. 



Art. XVIIL— Remarks on the Genus Tetradium, with Notices of the 

 Species found in Middle Tennessee ; by Prof. J. M. Safford 7 

 A. M., ^Geologist of the State of Tennessee. 



The genus Tetradium, has been characterized by Prof. Dana 

 in his great work on Zoophytes. -5 * His description and remarks- 

 are as follows : 



" Corolla massive, consisting of 4-sided tubes, and cells with 

 very thin septa or parietes ; cells stellate with 4 narrow laminae." 



" This genus is near Keceptaculites, but differs in having very 

 thin parietes and four distinct rays within the cells, one to each 

 side. The specimen answering to the description, is a fossil of 

 uncertain locality in the collections of Yale College, New Haven. 

 The cells are about half a line in breadth. The name, from the 

 Greek, tbtquq^ four, alludes to the quadrate structure." 



So far as we know, no further notice has been taken of this 

 genus. To us it is of great interest from the fact that individu- 

 als, belonging apparently to several species, are not very abund- 

 ant in the limestones of the Silurian, or as we shall hereafter term 

 it, the Central Basin of Middle Tennessee. 



In addition to the characters given above, we add the follow- 

 ing : The tubes, in the different species, vary from -J of a line 

 to nearly a line in breadth ; they are very long, and are most 

 frequently united throughout laterally, forming massive coralla 

 resembling more or less those of Favosites and Chsetetes ; some- 

 times however, they are united in single intersecting series, as in 

 Haly sites catenulatus, Linn. ; not unfrequently too the tubes 

 are isolated, or only united at irregular intervals, thus form- 

 ing loose fasciculated coralla resembling certain forms of Syrin- 

 gopora. 



The isolated tubes are nearly quadrangular, the edges being 

 more or less rounded. A slight linear depression down the mid- 



* United States Exploring Expedition during the years 1838, 1839, 1840, 1841, 

 1842, under the command of Charles Wilkes, U. S. % Vol. 8th, page 701. 



