139 
EXPLANATION OF PLATE IV. 
Fig. 1. Adult specimen with no plications, from Prasopora beds, Ottawa, Ont, 
“ 2. Average specimen with no plications, from Prasopora beds, Ottawa, Ont. 
“ 3. Adult specimen with one plication, from Prasopora beds, Ottawa, Ont. 
" 4. Average specimen with one plication, from Prasopora beds, Ottawa, Ont. 
“ 5. Specimen with one plication, from Indian Lorette, Que. 
" 6 and 7. Specimens with two plications, one primary and one implanted at a 
later stage of growth, from Prasopora beds, Ottawa, Ont. 
•* 8, 9, and 10. Specimens with two plications, formed by the bifurcation of one 
primary one, from the Prasopora beds, Ottawa, Ont. 
" 11 and 12. Specimens with two plications, formed by implantation, from the 
Prasopora beds, Ottawa, Ont. 
“ 13 and 14i Specimens with] three plications, one primary, two added later 
by implantation, from the Prasopora beds, Ottawa Ont.< 
“ 15. Specimen with three plications, one central primary one which is bifurcated, 
the third being implanted, from the Prasopora beds, Ottawa, Ont. 
“ 16. Specimen with three plications, two primaries, one implanted later, from 
the Prasopora beds, Ottawa, Ont. 
“ 17, 18, and 19. Specimens with three plications, two primaries one of which bi- 
furcated, from the Prasopora beds, Ottawa, Ont. ' 
“ 20 and 21 . Specimens with three plication?, two primaries one of which bifurcated , 
from the Fifth Avenue horizon, Ottawa, Ont. 
“ 22. Specimen with three plications, one primary one which has apparently later 
divided into three, from the Prasopora beds, Ottawa, Ont. 
" 23. Specimen with three plications formed simultaneously, from the Prasopora 
beds, Ottawa, Ont. 
“ 24. Specimen with three plications, one primary which has bifurcated, a third 
added later by implantation. The centre plication is about to bifurcate. 
From the Prasopora beds, Ottawa, Ont. 
" 25. Specimen with three plications, strong centre plication apparently about 
to bifurcate, initial stages obliterated, from the Prasopora beds, Ottawa, 
Ont. 
“ 26. Specimen with numerous side plications, from the Fifth Avenue horizon, 
Ottawa, Ont. 
“ 27. Specimen with four plications, formed from two by double but not sim- 
ultaneous bifurcation, from the Prasopora beds, Ottawa, Ont. 
“ 28. Specimen with four plications, three formed simultaneously one implanted 
later, from the Prasopora beds, Ottawa, Ont. 
“ 29. Specimen with four plications, central one bifurcated two implanted later 
at intervals, from the Prasopora beds, Ottawa, Ont. 
" 30. Specimen with numerous side plications, from the Fifth Avenue horizon, 
Ottawa, Ont. 
“ 31. An average specimen with fout plications from the Prasopora bod, Ottawa, 
Ont. 
“ 32. Specimen with five plications, formed by bifurcation and implantation, 
initial stages obliterated, from the Fifth Avenue horizon, Ottawa, Ont. 
" 33. Specimen with five plications, two strong ones, from the Prasopora beds, 
Ottawa, Ont. 
“ 34. Specimen with numerous side plications, from the Fifth Avenue horizon, 
Ottawa, Ont. 
“ 35. Specimen of Parastrophia. reversa (Billings) from Anticosti. Two plications 
formed from one by bifurcation. 
“ 36 Specimen of P. reversa (Billings) from Anticosti. Two plications formed 
simultaneously. 
“ 37. Specimen of P. reversa (Billings) from Anticosti. Three plications, two 
formed simultaneously the third implanted later. 
“ 38. Specimen of P. reversa (Billings) from Anticosti. Three plications, one 
being bifurcated. 
“ 39. Specimen of P. reversa (Billings) from Anticosti. Four plications formed 
simultaneously. 
