Miscellaneous. 391 



angular columns, three or four millimetres thick at the lower ends ; 

 between these are interpolated a good many smaller and shorter 

 columns. They all rapidly converge toward the centre of the oppo- 

 site concavity. Their sides are longitudinally striated, and covered 

 with punctiform impressions. Numerous small cross-bars connect 

 the columns, which are otherwise isolated from each other by a 

 narrow intervening space. 



The opposite side of the cavity, which forms the roof over the 

 convergent smaller ends of the columns, is free, but closely approxi- 

 mated to them, and bears the impression of fine concentric rings of 

 growth. This latter character is not very plain in my specimen, but 

 Goldfuss has given a very good figure of it. He thought it to be 

 the impression of the inner surface of a membranaceous envelope, 

 instead of taking it for what it is — the impression of the epitheca 

 surrounding the lower side of the corallum. 



The vermicular body, frequently noticed adhering to or penetrating 

 the root end of Pleurodyctium, is also seen in my specimen. 



I was greatly surprised at observing the same vermicular perfora- 

 tion in some small specimens of Michelinia, which also in all other 

 respects appear to be specifically identical with the coral of which 

 the European Pleurodyctium is a cap. 



The specimens were found in the shales of the Hamilton group, 

 Cayuga county, New York, and are in the possession of Prof. Winchell, 

 of Ann Arbor. They form small cakes, not much over one inch in 

 diameter. The lower side is almost flat, covered with a concentrically 

 wrinkled epitheca : the upper side is semiglobular, and shows the 

 mouth-ends of conical subangular tubes, the larger ones of which 

 measure from four to five millimetres. 



On the pohshed vertical sections of the coral, longitudinal strise 

 and rows of spinules, together with numerous side-pores, are visible 

 along the walls of the tubes. 



The upper part of the tubes is generally filled with calcareous 

 matter, and shows no diaphragms, which are only preserved in the 

 lower ends, and are in part simple and straight, in'part vesicular. 



The vermicular channel traverses the substance of the corallum, 

 irrespective of the direction of the tubes, and seems to cut straight 

 through them. After some flexures, it ascends to the upper surface, 

 and opens there with a round mouth, while the other tubes are more 

 or less angular. It is improbable that this perforating channel has 

 anything to do with the organism of the coral, and is more hkely 

 the work of a parasitic animal ; but after all, it is still strange to see 

 the majority of specimens, from such distant localities, attacked in 

 the same way by a boring animal. 



In the Corniferous Limestone at Port Colbome, on Lake Erie, I 

 lately found a cap exhibiting all the characters of Pleurodyctium. 

 In association with it numerous specimens oi Michelinia favositoidea 

 (Billiugs) are found ; and there remains no doubt that this cast 

 originates from a young specimen of this latter species.— <S»//mfln'« 

 Journal for January, 1863. 



