232 THE CANADIAN NATURALI6T,. |Vol. YU2 



Genus Amplexus, 



2. A. EXILIS. — Corallum more or less curved, expanding to a 

 diameter of 14 lines at 3J inches from the base. Surface "with 

 very distinctly defined costal striae, of whieh there are 5 in th« 

 width of 3 lines, where the diameter is about one inch, and 6 or 

 7 in the same space at the base. There are about 64 septa where 

 the diameter is 14 lines. The larger of these are scarcely a line 

 in depth ; the smaller about half that size. Thfi tabulae are very 

 thin, flat or slightly undulating, distant from each other from 1 

 to 6 lines. 



Owing to the fragile character of the shell, good specimens of 

 this species are rare. The best in our collection consist* of the 

 lower 6 inches partly imbedded in the rock. By the application 

 of acid, the whole of the interior has been completely freed from, 

 the limestone which filled it, so that it shows the tabulae and 

 septa perfectly. It is curved, somewhat irregularly, to a radius 

 of between 4 and 5 inches. There are numerous small rings of 

 growth, in general not very prominent, but with some that are 

 angular and strongly elevated. These are, sometimes, so deep 

 that they give to the costal striae, a nodose appearance. 



The extremely rudimentary state of the septi, distinguishes 

 this species from all the described American forms known to me» 



Occurs in the Corniferous. 



3. A. MiRABiLis. — Corallum sometimes abruptly curved in 

 diiFerent directions, expanding to a width of from 15 to 20 lines 

 in a length of 4 or 5 inches from the base ; above which it be- 

 comes more nearly cylindrical. Surface with fine engirdling 

 striae, in general 4 or 5 in the width of 2 lines,, but in some 

 places, the same number occur in the width O'f G«ie line. There 

 are also numerous angular rings of growth, distant from 2 to 15 

 lines from each other, with sub-concave spaces between. Septal 

 costas rounded, distinctly defined by sharp striie between them, 

 7 or 8 in the width of 3 lines near the base, and 4 or 5 in the 

 same near the calice. There are about 40 Inrge septa at the 

 calice, where the diameter is about 18 lines, with the same num- 

 ber of small ones between them. The larger have a depth of 3 

 or 4 lines and the smaller 1 line. All of the septa are more or 

 less curved, sometimes very tortuous. The tabulae have not 

 been observed. 



The above description was drawn up from a specimen, llL 



