14 Contributiom towards Estahlishing the General Character 



together with another at present in the Sunderland Athenaeum, were ob- 

 tained from three separate but nearly contiguous sinkings at North Bid- 

 dick Colliery, on the Wear, at a depth of 140 feet below the surface. 

 They were found in a perpendicular position, each with its base or root- 

 stock resting on a thin layer of impure coal, not exceeding three inches 

 in thickness. The stratum in which these specimens were imbedded con- 

 sists of a greyish-coloured arenaceous shale, passing into a carbonaceous 

 state at its junction with the subordinate coal-seam. The material of 

 which the specimens are composed is the same as their matrix. 



The most perfect stem, and the one to which the following remarks 

 will be confined, is 7 feet 6 inches in height : its diameter is not uniform 

 throughout ; at the base it is 2 feet three inches ; two feet higher, it is 

 1 foot 10 inches ; from this part the thickness rapidly increases to about 

 one-third of the height of the specimen, where it is 2 feet ; at this point 

 the diameter becomes suddenlj^ reduced to 1 foot 6 inches, which thick- 

 ness is preserved until within a foot of the top, where another increase 

 takes place. The increase of diameter at the top appears to be due to 

 the stem dividing itself into eight or nine branch-like divisions. Unfor- 

 tunately these supposed branches are broken off so much below their 

 actual departure from the main stem, as to afford only a slight indication 

 of their existence. This character, was, however, more obvious in the 

 Sunderland specimen ; but, unfortunately, circumstances not allowing 

 of its being permanently placed when it was first obtained, the part 

 which exhibited the branches has been destroyed. In support of Sigil- 

 laria having had a branching stem, I may here mention, that a specimen 

 which was sent to Mr Hutton for examination by Mr Dawes of Manches- 

 ter, was clearly a branch which had been broken off at its junction with 

 the parent stem. Some other specimens sent by the same gentleman 

 exhibited a similar character ; and Brongniart mentions that the Kunz- 

 werk specimen, previously alluded to, was divided into two equal 

 branches. In consequence of a horizontal fracture occurring at that 

 part of the stem where, as before mentioned, the diameter becomes sud- 

 denly increased, it may be supposed that this augmentation is due to 

 the fracture, especially as the same is observable on the other specimen 

 in the Newcastle Museum. I am inclined, however, to think that it is 

 due to the stem being unequal in its horizontal growth. 



All the specimens are distinctly ribbed and furrowed longitudinally. 

 The most perfect one in this respect has some of its ribs furcated ; in one 

 instance there are two furcations on one rib; by this means the ribs be- 

 come considerably narrower at the top than at the bottom; in general, 

 however, this diminution is caused by the ribs decreasing gradually in 

 width in the ascending direction ; at the base where they are nearly 

 obsolete, the average width is about three inches, but at the top, where 

 they are distinctly marked, it is reduced to less than an inch. On the 

 middle of each rib is a row of scars in triple series, that is, three are 

 placed in close contact with each other in a horizontal du-ection. The 



