7 



more precipitous than those on the south-west. In this they accord with 

 the general character of the undulations in the Lower Silurian strata south 

 of the St. Lawrence. The strikes of the anticlinal beds are not precisely 

 parallel, but converge towards the south-east ; from which it results that 

 the ridges or crowns of the folds have a slope in that direction. 



ZOOPIIYTA. 

 Zaphrentis incondita. (N. sp.) 



"Undetermined species of Zaphrentis^'' Geo-. Can., p. 393 

 PI. 1, figs, 1, la, 16. 



Description. — Corallum simple, turbinate and strongly curved at the 

 base, becoming cylindrical above ; nine or more inches in length and 

 over two inches in diameter. From the acute base upwards it expands 

 to a thickness of about fifteen lines in a length of two inches, and to 

 twenty-four lines, in four inches ; above which the body of the coral 

 becomes more nearly cylindrical, or only very gradually increasing in dia- 

 meter. Surface with numerous engirdling ridges of various sizes, the 

 larger are from half a line to five lines in width, and are often angular 

 on their crests. Upon these larger ridges and in the grooves between 

 them are numerous smaller ridges or transvere striae, generally two or 

 three in a width of one line. The longitudinal, or septal striae, are in 

 general only obscurely seen, being obliterated by the transverse grooves ; 

 there are five or six of them in the width of three lines. 



In the interior of the coral, the radiating septa reach the centre in the 

 basal portion. But, above a diameter of one inch, there is a large space 

 in the centre (as shown in fig. la) occupied by the transverse diaphragms 

 alone, the septa not extending more than half an inch inward. There 

 are two sets of them, the smaller projecting inward rarely to the depth 

 of one line. There is one of the smaller between each two of the longer. 



The transverse diaphragms are well developed. They are much undu- 

 lated in the central portion (as shown in fig. \h) and strongly curved 

 downwards near the exterior. There appear to be ten or twelve of them 

 in the length of one inch ; but, owing to their undulations, there are some- 

 times places in which they are separated to the distance of two or three 

 lines, while elsewhere they may be nearly in contact. The septal fossette 

 has not been observed. 



Varieties. — Occurrin^^ alono; with the above is a somewhat more slender 

 form with, in a general way, the same external character?, but with the 

 transverse diaphragms more regular and the septa extending inward 



