378 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 4, 



3. On an ORTHOCERAs/rom China. 

 By S. P. Woodward, Esq., F.G.S. 



(Plate VI.) 



The specimen in question is one of several that were obtained by 

 Mr.' Lockhart of Shanghae, from some place 200 miles distant, and 

 transmitted by him in 1854 to Daniel Hanbury, Jun., Esq., of Plough 

 Court. They are longitudinal sections in thin plates of limestone, 

 and seem to have been used as screens, for they were mounted in 

 carved- wood frames with stands. The same gentleman at an earUer 

 period communicated some Devonian Brachiopoda, identical with 

 French and Belgian species, described by Mr. Davidson in the Geo- 

 logical Journal, 1853, p. 353. 



The largest specimen measures in length 29 inches, and 4 in its 

 greatest diameter ; it wants the last chamber and about 5 inches of 

 the spire. The angle of the spire is only 6°, and the intervals be- 

 tween the septa vary from ^ to less than \ the diameter of the cells. 

 The siphuncle is central and quite simple. 



The most instructive specimen is smaller, measuring 18 inches in 

 length and 4 in diameter ; it only wants the last chamber (see PL VI. 

 fig. 1). The angle of the spire is 12 degrees, and the depth of the 

 chamber is from ^ to less than \ their diameter. 



The siphuncle is filled with dark reddish-brown limestone ; the air- 

 cells are lined with white spar and filled with converging crystals of 

 the same, or with greenish-grey stone. The shell has been entirely 

 replaced by grey stone, recording its outline and thickness, except in 

 some of the thinner septa which are only indicated by curved lines. 



The siphuncle is simple, central, and incomplete ; the shelly part 

 of the tube {s) extending only one-third of the way from the con- 

 vexity of each septum towards the concavity of its predecessor. In 

 the last seven chambers, only two of which {a, a) are represented in 

 the figure, the siphuncle appears to have been completed by a mem- 

 branous tube {t), which has disappeared from those of the spire. 



In the last of these chambers, with an incomplete siphuncle (6), 

 the lining membrane appears to have separated a small space from 

 the wall, equally all round ; this space being filled with spar, whilst 

 the general cavity of the chamber is occupied by red stone, like the 

 siphuncle. 



In the next chamber the separation and contraction of the lining 

 membrane has proceeded to a greater extent ; and so on in each suc- 

 cessive chamber, until the fifth, after which the siphuncle seems re- 

 placed by it, and gives oif on each side a process directed towards the 

 anterior angle of the cell. The originally membranous nature of 

 this tube (formed by the contracted lining of the air-cells) is shown 

 by its want of symmetry. Towards the apex of the fossil it is black, 

 as if carbonized. The space (c, c) between the true shell and its 

 lining membrane is lined with spar, and sometimes filled with it, as 

 before mentioned ; but in some instances the limestone has pene- 

 trated, after the dissolution of the shell. 



The changes which this specimen has undergone appear to be 



