85 THE PALEONTOLOGY OF MINNESOTA. 
[Streptelasma. 
STREPTELASMA PROFUNDUM (Coni'ad ms.) Owen. 
PLATE G, FIGS. 17-19. 
1844. Cyathophyllum profundum OwkrNn. Geological Exploration of Iowa, Wisconsin and Illinois, 
pl. 16. fig. 5. 
1847. Streptoplasma profunda HAuu. Palwontology of New York, vol. i, p. 49. 
1847. Streptelasma profunda HALL. Ibidem, pl. 12, figs. 4a-4d. 
1857. Streptelasma profunda BILuLINGs. Canadian Naturalist and Geologist, vol. i, p. 123, figs. 7, 8. 
Original description —‘“Obliquely turbinate, often slightly curved near the base, 
expanding above more or less abruptly ; cell profoundly deep, extending nearly to 
the base of the coral ; margin of the cup reflexed ; surface scarcely marked by trans- 
verse ruge ; lamella from 36 to 60, strong, nearly equal on the margin, but distinctly 
alternating in length within ; no transverse dissepiments or celluliferous structure.” 
Billings probably was the first to point out that the three primary septa of 
Streptelasma are plainly indicated on the outside of the corallum from which the 
other septa branch. He says: “The mode of growth of these corals [S. corniculum 
and S. profundum] 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 lamella; 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 lamellie are very conspicuous above the 
others on the inside of the cup, and on the outside their position is marked by three 
upright seams extending from the top to the bottom, and from each side of which 
the newer lamellw may be seen branching away.” 
In the Canadian specimens of this species the corallum “is very little or not at 
all curved,” and the same is true of Minnesota individuals occuring in the Trenton 
limestone and the lower portion of the shales immediately above. In Wisconsin, 
however, where it is quite abundant near the base of the “Upper Buff” beds in well 
preserved specimens, the curvature is more often as great as in S. corniculum Hall. 
The point of attachment in these is often well shown, but is generally smaller than 
in that species. 
S. profundum can be readily separated from 8. corniculum by its profoundly deep 
visceral cavity, smaller number of distinct crenulated septa which are never twisted 
in approaching the center and in the more sharply defined lateral fossula and greater 
development of the four primary septa. Billings gives the number of large and 
small septa in adult Canadian examples as about seventy-four, and this likewise is 
true for Minnesota specimens, while those from Wisconsin vary between 60 and 72, 
The greater variation mentioned by Hall, “lamelle from 36 to 60,” is probably due 
to young examples, which always have a smaller number of septa than adult speci- 
mens, 
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