ASTROPECTEN. 119 



slate, even if the litholoo-ical character of the matrix in which the fossil lies had not of 

 itself been sufficiently characteristic of that formation. 



"The Star-fish forwarded to Mr. Bone was found by me on the 13th of April, 1853, 

 in the parish of St. Martin, in Stamford, which parish stands in Northamptonshire, sepa- 

 rated from the other paiis of the town by the river Welland, which at this point divides 

 the counties of Northamj)ton and Lincoln. There is a very curious fact in connection with 

 the beds upon which Stamford and St. Martin's stand. The valley of the Welland, which 

 separates the old town from its outlying parish, narrows at this point almost to a gorge, 

 and the ground rises steeply on either side. On the northern or Lincolnshire side the 

 surface rises throngli and at the back of the town to an elevation of from 150 to 200 

 feet above the level of the river, and the strata of which this hill is composed consist of 

 the Cornbrash ; capping the higher elevation of the district is a thick bed of variegated and 

 stratified clays equivalent to the Bradford clay. A series of beds of the Great Oolite, 

 attaining a great thickness, and having as their lowest member a slaty bed occasionally 

 very fossiliferous, and proved, I believe, to be equivalent to the Stonefield slate of Oxford- 

 shire, Beneath these are the white, siliceous sand of the Inferior Oolite, and the Oolitic 

 rock of the same formation, strongly impregnated with iron. Under all, and forming the 

 basement bed of the district, lies the Lias clay, of unascertained thickness. The beds I 

 have enumerated preserve, as nearly as may be, their horizontal position ; they are inter- 

 sected more or less by fissures, but otherwise exhibit little evidence of disturbance. 

 Upon the Northamptonshire side, however, an upheaval has taken place, throwing up the 

 lower beds to the top of the hill, and disturbing their horizontal position. The upper beds 

 of the series are wanting on this side, but a huge fragment seems to have separated from 

 the upheaved mass, and to have subsided into the chasm formed by the convulsion. 



" Upon this fragment St. Martin stands ; it is about three quarters of a mile in length, 

 east and west, by about half a mile in width, north and south ; its beds preserve nearly their 

 original horizontal position, but they are divided near their western extremity by a fault 

 running north and south. 



" Thus, in proceeding from the river southward (up the hill), we have the Lias clay at 

 the bottom, then the ironstone of the Inferior Oolite and its overlying sands, then the 

 siafe bed — Stonesfield slate — and over this some of the very various beds of the Great 

 Oolite. Still rising the hill, we come again to the Lias clay, the ironstone, the sands, slates, 

 and Great Oolite, in a reiterated succession ; but in this second series we have what we 

 had not before observed, a bed of clay lying between the beds of the Great Oolite and 

 the beds of the Inferior Oolite, and which clay, from its position, I suppose to be equiva- 

 lent to the Fuller's earth. 



" It was in the slate bed of the loioer series above described that I found the Astropecfen 

 in what is locally called a "pot-lid." The lower beds of slates consist of masses of a 

 flattened, semi-spherical foriu, lying with their convex surfaces downwards on the under- 

 lying bed of sand, in the hollows of which, it would seem as if they had been moulded. 



