1873.] SHARP OOLITES OF HORTHAMPTONSHIRE. 241 



Many years ago, in an adjacent working, I obtained during one 

 of my pleasantly remembered excursions in the company of Prof. 

 Morris, a fragment of the upper surface of the red oolitic bed of 

 this section, which had been profusely perforated by a small boring 

 bivalve. 



In .the Ferruginous beds of the Northampton Sand, casts of the 

 crypts of Lithodomus inclusus, Phil., generally including the shell, 

 are very abundant, and sometimes large, but are always found asso- 

 ciated with masses of coral. On the other hand, in the limestones 

 of the Great Oolite, casts of the crypts of Pliolas occur, not so asso- 

 ciated. As no coral has been found in connexion with these borings, 

 I am disposed to conclude that they are the work of Pliolas rather 

 than of Lithodomus. At any rate, I would agree with the conclu- 

 sion arrived at by Prof. Morris, as stated in his admirable article in 

 the ' Geological Magazine' for March, 1869, that these perforations 

 " clearly indicate a period of arrested deposition in this old sea-bed ; 

 during which these mollusks lived and inhabited the surface of the 

 subjacent rock, already partly consolidated." 



The newer and larger excavations at Ketton are near the base of 

 an escarpment facing north-east. The section presents a thickness of 

 beds of some 20 to 23 feet. The upper portion, to the depth of 

 about 15 feet, consists of the clays of the Upper Estuarine Series, 

 in three beds (as in the last section), viz. grey clay, whitish clay 

 (with vertical yellow markings, as of root perforations), and a very 

 compressed, thinly-laminated, and somewhat bituminous clay, inter- 

 calated with thin seams of brown and white sand, and having the 

 ferruginous band at the base. The lower portion consists of Lin- 

 colnshire Limestone; the upper two beds of which, having together 

 a thickness of from 5 to 6 feet, are oolitic freestone. The upper 

 bed,* being red, coarse, and perishable, and known as " Elesh " or 

 " Crash " by the quarrymen, is rejected : the lower bed is the cele- 

 brated Ketton freestone. Beneath the freestone, is a shelly " Pag " 

 bed, not worked, but probably about 4 feet in thickness ; and under- 

 lying this, is a harder oolitic limestone having a glistening fracture, 

 which also is not worked, and its thickness is uncertain. I have 

 obtained from this bed, Gypricardia Bathonica, d'Orb., and Phola- 

 domya fidicida } Sow. 



As the works proceed, and an advance is made into the mass of 

 the hill, the section will deepen by an accession to the thickness of 

 the Upper Estuarine clays. The high ground above has a capping 

 of Great Oolite limestone. 



Details of Section at the Newer Excavations, Ketton. 



1. Upper Estuarine Series — ■ 



ft. in. ft. in, 



a. Grey clay 3 6 



b. Whitish clay, with yellow vertical markings, like 



root perforations 4 G 



c. Very compressed and somewhat bituminous clay, 



in very thin layers, intercalated with thin seams 

 VOL. XXIX. PART I. R 



