214 TWENTIETH REPORT ON THE STATE CABINET. 



of the polyp. The prevailing form of the stipe is somewhat concavo- 

 convex, with the centre of the concave side prominent ; the entire surface 

 is covered by a net-work of corneous substance, and the cell-apertures are 

 quadrangular. 



Prof. GrEiNiTZ has given some further illustrations, showing more em- 

 phatically a longitudinal axis on the convex side, to which are joined the 

 cell-partitions ; while he regards the common body as occupying the pro- 

 minent central portion of the concave face of the stipe, and showing the 

 cell-partitions terminating before reaching the centre, leaving a space 

 occupied by the width of the common body. This he represents as covered 

 by a net-work of slightly different texture from that of the other portions 

 of the substance. 



The Canadian specimens which I have referred to this genus are so 

 extremely attenuated that it is impossible to determine the details of 

 structure, and the surface-characters are obscure. Thus far w^e have no 

 American specimens in a condition to afford the means of elucidating some 

 obscurities, which seem to me still to exist, in regard to the intimate struc- 

 ture of this genus. The species of the Clinton formation is extremely 

 compressed ; and while some specimens show the cell-divisions terminating 

 at a distance from the centre, yet, after protracted and repeated examina- 

 tions, my most critical observations result in showing only the structure 

 which is illustrated on Plate i, figs. 20 and 21. 



On one side we have an external, cylindrical, solid axis, to which the 

 cell-divisions are joined ; but these latter show only a filiform cylindroid 

 process, extending from the axis to the cell-margin, and projecting a little 

 beyond the margin of the stipe. The only other aspect which we observe 

 in this species is that of an undulating or zigzag filiform axis on the 

 opposite side, to which the cell-partitions are joined, as in fig. 21, Plate i. 

 We know this to be on the opposite side or within the stipe, as it is 

 sometimes seen overlying the straight axis and cell-partitions. 



At the junction of the cell-divisions with the zigzag axis there are other 

 processes of similar character, projecting upward and outward from the 

 axis, all of nearly equal length, but apparently broken at their extremities. 

 I have not been able to determine any connection between these and other 

 parts of the skeleton, but we have the two structures very clearly repre- 

 sented in the figures referred to. I have supposed that similar processes 

 may have extended to the opposite side, from the junction of the cell- 

 partitions with this undulating axis, either joining the cell-divisions or the 

 straight axis; but after long investigation, I have been unable to find 

 satisfactory evidence of such connection. The cell-apertures are sur- 

 rounded by thickened margins, and the only appearances of cell-partitions 

 are the sub-external cylindrical extensions from the aperture to the axis. 

 Neither the species of the Quebec group nor that of the Clinton formation, 

 in any of the specimens seen, are in a condition to show evidence of the 

 concavo-convex character of the stipe represented by M. Barrande and 

 Prof. Geinitz. 



