Fossil Corals, — Lower Siluiian Rocks of Canada. 123 



'belong to this species, there are from 60 to 90 lamellaj to be seen on the 

 outside of the cup at the margin. In those which are empty the cavity once 

 occupied by the inner sack mentioned in the preceeding pages, extends 

 downward from one fourth to one third of the length of the fossil. On tho 

 outside the lamclla3 are seen to branch from the sides of a line running from 

 the top to the bottom along the convex, curved side, and again from two 

 other similar lines at the sides. 



This species occurs in the Trenton Limestone, and is somewhat common 

 in the rock at the Barrack Hill at the city of Ottaw^a. The specific name 

 [corniculum] is from the Latin, " a little horn." 



Streptelasma profunda, (Hail.) 



In this species the -cwp is very little, or not at 

 all curved. The length is about an inch and a half 

 in full grown specimens, and the cavity within 

 extends sometimes nearly to the bottom, hence the 

 name {profunda,) " profound" or " deep." There 

 are about 74 lamellae in specimens of the size repre- 

 sented in Fig. 7. They are usually small, and large 

 alternately. The small ones are those newly deve- 

 loped, and not full grown. 



This species occurs in the Black River and 

 Bird's Eye Limestones, at the base of the Trenton. 

 Fig. 7. — Streptelasma profunda. 



In addition to the above there are several other species in the Trenton 

 Limestone which we shall endeavour to figure hereafter. They are S. crassa 

 with about 50 thick coarse lamella, S. muItUomellosa with about 120 

 lamelte, and S. parvida with only about 30. The latter is very small, and 

 all resemble very much S. corniculm. Crassa, thick ; midtilamellosa, " many 

 lamellse ;" and parvula, small. 



The mode of growth of these corals appears to have been as follows : — 

 At first they consisted of a mere point attached to the rock, when the cup 

 commenced to form there were only four partitions or lamelte, as it increased 

 others were added, three of the original ones continuing to grow, and the 

 fourth being undeveloped. In good empty specimens of S. profunda the 

 three large primary lamelte are very conspicuous above the others on the 

 inside of the cup, and on the outside their position is marked by three upright 

 Beams extendi ng from the top to the bottom, and from each side of which 

 tlie newer lamellae may be seen branching away. One of those is seen in the 

 front of Figure 7. 



These cup shaped corals with the four primary 

 lamellae commenced their existence in the seas of the 

 Lower Silurian age, but became extinct in the Permian. 

 To this important fact we shall return hereafter. 



Fig. ^.—Interior of {S. profunda,) shewing tkt 

 three large primary lamellce. 



