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HARDWICKE'S SCIENCE-GOSSIP. 



on shale or as sandstone and ironstone casts. This 

 is probably owing to their impressions having a close 

 resemblance to Calamites, while their sandstone casts 

 might be easily confounded with those of Calamites, 

 Lepidodendron, and other fossil plants. Being con- 

 vinced that they must occur as ordinary fossils, I 

 have lately subjected all specimens of fossil plants 

 which I have met with to a more careful scrutiny, 

 and the result has been that I have found specimens 

 of Astromyelon both as sandstone casts and as im- 

 pressions on shale. 



A short time ago, while geologising with a friend 

 in the flagstone quarries of Ringby, near Halifax, 

 I saw a beautiful fragment of Astromyelon on the face 



The transverse section of a typical specimen shows 

 a central parenchymatous medulla, surrounded by a 

 woody cylinder, which is composed of a regular 

 series of primary wedges. These wedges are almost 

 identical in structure with those of Calamites, with 

 the exception of the absence of the canals at their 

 inner ends, which are also somewhat more obtuse 

 than are those of Calamites. The number of wedges 

 forming the exogenous cylinder varies from five or six 

 in very young specimens, to from nine to thirteen in 

 more mature forms. In Calamites the wedges are 

 more regular in size, and vary from eleven to sixty or 

 more in number, according to the size of the plant. 



In Astromyelon the wedges vary considerably in 



Fig. 143- — Longitudinal section of Astro- 

 myelon. «, woody cylinder; />, pith. 



fig. M=.-Astromyelon, W.lliamson. From a specimen in writer's cabinet. 



X 24 diam. 



of a flagstone. It was the impression of a longitudi- 

 nal section of a portion of the stem, which showed 

 the structure almost as perfectly as a coal-ball section. 

 The mural arrangement of the cells of the medulla— 

 so familiar to us in our sections— presented the 

 appearance of a wall of white bricks, while the base- 

 ment-layer and copings of the wall were represented 

 by the narrower and darker and more compact layers 

 of the ligneous zone. The fragment was impressed 

 on a filmy layer of shale, and broke into smaller frag- 

 ments when I attempted to secure it. It is evident 

 from this fact that the remains of this plant must 

 either have been overlooked or confounded with those 

 of other fossil ])lants. 



The coal-ball material in the neighbourhood of 

 Halifax has yielded a great variety of these Astro- 

 mytlons. 



Fig. 144.— Part of one of the tubular spindle-shaped vessels of 

 the ligneous cylinder of Astromyelon. 



Size, sometimes even in the same plant. Each wedge 

 is composed of a number of lamince, or rows of 

 vessels, which are arranged in a radiating manner, 

 and each lamina is again composed of a number of 



