88 REPORT—1863. 
aid in determining species and also in grouping families of the Mollusca would he 
the result. Hinge-teeth, which were persistent in form, could be indicated by or- 
dinary numerals, and variable teeth by accentuated numerals. In drawing out such 
a scheme care was taken to note the position of the teeth, whether anterior or pos- 
terior to the umbo. He considered that the plan, if adopted, would simplify the 
definition of a genus. 
[The paper is printed in the ‘ Geologist’ for February 1864. ] 
On a Section of the Strata from Hownes Gill to Cross Fell. 
By T. Sopwirn, B.S. 
The strata of the lead-mining districts of the North of England extend from 
beneath the coal-bearing strata of the Northumberland and Durham coal-fields at 
Hownes Gill to the mountain of Cross Fell in Cumberland, and were exhibited in 
a section taken from east to west over the important lead-producing districts of 
East and, West Allendale and Alston Moor. The Fell-top Limestone is seen to form - 
nearly the summits of the highest hills, and, beneath, a great thickness of siliceous 
and argillaceous strata intervenes between it and the Great Limestone, This forms: — 
one of a series of limestone strata, in which large quantities of lead have.been pro- 
duced. Several details relating to this section were verbally explamed by My. 
Sopwith. Op 
On Models illustrating Contortions in Mica-Schist and Slate. 
By H. C. Sorsy, BS. 
One of the models was formed of alternating bands of black and grey vulcanized 
india rubber, which were firmly held at one end by a brass clamp, and were free at 
the other, unless held by the fingers. When this was bent, it showed that the ex- 
terior layer was stretched and the inner compressed. Yielding in this manner, no 
secondary contortions were produced, but merely a simple band, as in contorted 
slate rocks. The other model was constructed with alternating bands that could 
not be stretched or compressed, by making use of the india-rubber enclosing can- 
vas, and was firmly held at both ends by brass clamps; and, when this was bent, 
various secondary contortions were produced, similar to those met with in many 
varieties of contorted mica-schist. 
Description of a Sea-star, Cribellites carbonarius, from the Mountain Lime- 
stone Formation of Northumberland, with a notice of its association with 
Carboniferous Plants. By Grorcr Tarr, F.GS. 
This Asteroid, the first recorded from the Mountain Limestone, is an impression 
of the upper surface, in a fine-grained micaceous sandstone. It is named Cribel- 
lites carbonarius ; and the following characters are observable :—Rays five, rounded, 
lanceolate, five times as long as the disk, ridged in the centre, covered with longi- 
tudinal rows of reticulating tubercles: disk small and tuberculated. The disk is 
only 0:3 of an inch in diameter, while the rays are 1:5 inch in length. A circular 
impression in the disk may be the impression of the Madreporiform nucleus. In 
the form of this Asteroid, and in the characters observable, it is similar to Cri- 
bella rosea, Miller; but the rays are proportionally longer, the disk smaller, and 
the tubercles much nearer to each other than in the recent analogue. The sand- 
stone from which the fossil Sea-star was obtained lies 20 feet above the Shilbottle 
coal, and about 600 feet below the base of the millstone grit, being in the upper part 
of the Mountain Limestone formation, which, in Northumberland, is about 3000 feet 
in thickness. In this sandstone there also occur Strophomena crenistria and the 
remains of carboniferous plants. In the same locality, somewhat higher in the 
series, there is another sandstone-bed, in which are vast numbers of Strophomena 
crenistria, associated with species of Sigillaria, Lepidodendron, Calamites, Knorria, 
and the Stigmaria jicoides. One or two other similar facts will help to illustrate 
the geological history of the Coal era. At Budle a metamorphosed shale, 30 feet 
in thickness, overlying a limestone, is in the under layers crowded with marine 
organisms, such as Griffithides farnensis, Euomphalus carbonarius, Bellerophon Uri, 
