45U 



desideratum in nomenclature, and as no such fossil appears to have 

 been described or figured, we have named it ' Lyginodendron Laiuh- 

 hurgii ; ' forming the generic name from Xvyivos, wicker-work, and 

 SevSpov, a tree ; and dedicating it by its specific name to its discoverer, 

 Mr LandsborougL" The fragments of the fossil were spread over 

 a space of about two yards, and have not been observed, except in 

 that place. The finest specimen obtained was about 18 inches in 

 length, by 3 in breadth. It was discovered in the middle stratum. 



Of the genus SigiUaria there are two or three varieties, as Siffil- 

 laria oculata, SiffiUana reniformis, &c &c. 



The most magnificent fossil found in the quarry is the Boihroden- 

 dron pundatum. A splendid specimen of this fossil is in the pos- 

 session of ^Ir Landsborough, which he describes to be of a size and 

 weight which he can scarcely lift from the ground. It is extremely 

 rare, however ; only two, or at most three, examples of it have been 

 procured. 



Another very curious and remarkable fossd also, is the Sti/loliihen, 

 of which there appears to be two distinct varieties — one with very 

 broad stripes, the other with the lines more closely approxunating, 

 and, likewise, more deeply indented. 



Specimens of all the before-mentioned fossils were contained in 

 the collection presented to the Society. The author presented at the 

 same time some masses of impure ironstone, from a coal-pit on the 

 same estate, containing very beautiful specimens of the Unio Un'l. 



2. On a new Self-Eegistering Barometer. By Eobert Bryson, 

 F.E S. 

 From the nature of the instrument, it is impossible to give an 

 intelligible abstract of the paper. Tlie paper, with a description of 

 the instrument, and a statement of its indications for some months, 

 is piiblished in the Society's Transactions. 



Monday, loth January ISJri. 

 Dr ABERCEOMBIE, Y.P., in the Chair. 

 The following Communications were read : — 

 1. On the Vibrations of an Interrupted Medium. By Pro- 

 fessor Kelland. 



The object of this paper was the approximate determination of the 

 change of phase, and intensity of a ray reflected at the surface of a 

 medium, which admits of no refraction. 



