258 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. [May 8, 



minerals, — objections which, however plausible in the case of highly 

 crystalline rocks, in which organic remains may be simulated by 

 merely mineral appearances readily confounded with them, are 

 wholly inapplicable to the present specimen. 



1. General Appearance. — The fossil is of a clavate form, six and a 

 half inches in length, and about four inches broad. It is contained in 

 a slab of dark-coloured, coarse, laminated limestone, holding sand, 

 scales of mica, and minute grains and fibres of carbonaceous matter. 

 The surface of the slab shows a weathered section of the fossil 

 (PI. XI.) ; and the thickness remaining in the matrix is scarcely 

 two lines, at least in the part exposed. The septa, or plates of the 

 fossil, are in the state of white carbonate of lime, which shows their 

 form and arrangement very distinctly, in contrast to the dark stone 

 filling the chambers. The specimen lies flat in the plane of strati- 

 fication, and has probably suffered some compression. Its septa are 

 convex toward the broad end, and somewhat undulating. In some 

 places they are continuous halfway across the specimen ; in other 

 places they divide and reunite at short distances. A few transverse 

 plates, or connecting columns, are visible ; and there are also a 

 number of small veins or cracks passing nearly at right angles to 

 the septa, and filled vdth carbonate of lime, similar in general ap- 

 pearance to the septa themselves. 



On one side, the outline of the fossil is well preserved. The narrow 

 end, which I regard as the basal portion, is rounded. The outline 

 of the side first bends inward, and then outward, forming a graceful 

 double curve, which extends along the greater part of the length. 

 Above this is an abrupt projection, and then a sudden narrowing ; 

 and in the middle of the narrow portion, a part has the chambers 

 obliterated by a white patch of carbonate of lime, below which some 

 of the septa are bent downward in the middle. This is probably 

 an effect of mechanical injury, or of the interference of a calc-spar 

 vein. 



"With the exception of the upper part above referred to, the septa 

 are seen to curve downward rapidly toward the margin, and to 

 coalesce into a lateral waU, which forms the defined edge or limit 

 of the fossil, and in which there are some indications of lateral 

 orifices opening into the chambers. It is worthy of remark that, in 

 this respect, the present specimen corresponds exactly with that 

 which was originally figured by Sir "W. Logan in the ' Geology of 

 Canada,' p. 49, and which is the only other specimen that exhibited 

 the lateral limit of the form. 



On the side next the matrix, the septa terminate in blunt edges, 

 and do not coalesce ; as if the organism had been attached by that 

 surface, or had been broken before being imbedded. 



2. Microscopic Characters. — Under the microscope, with a low 

 power, the margins of the septa appear uneven, as if eroded or 

 tending to an acervuline mode of growth ; but occasionally the septa 

 show a distinct and regular margin. For the most part merely 

 traces of structure are presented, consisting of small parts of canals, 

 filled with the dark colouring-matter of the limestone. In a few 



