248 Prof. T. Rupert Jones and J. W. Kirkhy— 



cracks seen on the surface of American cloth in railway-carriages can 

 be accounted for in the same way. 



These and many other facts, which I will not now adduce, have 

 led me to the conclusion that while the first series of straight cracks, 

 which often produce columnar structures in rocks, owe their origin 

 to the contraction which takes place during cooling, the secondary 

 systems of curved cracks, which give rise to the perlitic and similar 

 structures, are more probably due to the contraction which goes on as 

 the volatile materials which they contain are slowly separated from 

 them. I hope to adduce some further illustrations of this principle 

 on a future occasion. 



II. — On Carboniferous Ostracoda from the Gayton Boring, 

 Northamptonshire. 



By Prof. T. Rupert Jones, F.R.S., and James W. Kirkby, Esq. 



(PLATE VII.) 



THE Carboniferous Ostracoda here described are from the deep 

 Gayton Boring, near Northampton. Hand-specimens of the 

 rock, obtained by H. J. Eunsbn, Esq., F.G.S., were given to us by 

 B. Etheridge, Esq., F.B.S., some months ago ; and Mr. Eunson 

 kindly gave us another piece lately. 



To explain the situation of the bore, as well as the position of the 

 Carboniferous strata in it, we quote as follows from Mr. H. J. 

 Eunson's paper "On the Palaeozoic Bocks beneath Northampton," in 

 the Quart. Journ. Geol. Soc. vol. xl. 1884, p. 485, etc. : 



"The second trial took place near the village of Gayton, five miles 

 south-west of Northampton, not far from the Banbury-lane crossing 

 of the L. and N.-W. Bailway, about two miles north-west of Blis- 

 worth Station (see Ordnance Map 52 S.W.). It was thought that, 

 under the known attenuation of the Trias westward, the Waterstones 

 could be found, if only the site selected was at a sufficient distance 

 beyond the Carboniferous rocks to have allowed the lower beds of 

 the Triassic series to be deposited near Northampton. 



" This boring, 282 feet above sea-level, was commenced at the 

 junction of the Upper with the Middle Lias, followed by the Lower 

 Lias clays, the aggregate thickness of which was 581 feet." 



The White Lias and BliEetic beds, 36 feet thick, are described as 

 resting on a slightly eroded surface of the Triassic strata, which are 

 82 feet 6 inches thick. The lowest of these latter contained much 

 debris of Carboniferous rocks. These last began, in the boring at 

 699 feet, with the eroded Carboniferous Limestone. From about 31 

 feet 6 inches lower down was brought up a bluisb-grey shale ; and 

 from a little below that a greenish-grey shale. The former has yielded 

 the little fossils here described. The latter contains similar Microzoa. 

 The boring was continued into the Old Bed Sandstone, and to a 

 depth of 994 feet, without getting the supply of water sought for. 



The minute specimens under notice were obtained for us by Mr. 

 C. D. Sherborn by breaking and washing the rock in which they had 

 been imbedded. There is a fair quantity of them, — certainly a few 



