346 J. F. BLAKE AND W. H. HT7DLEST0N ON 



which contains a mass of fossils glued together in a dense ferru- 

 ginous limestone with hard cores, indicative of its coral origin. 

 The following, in very bad condition, were noted — Natica, Nerincea, 

 Chemnitzia, Phasianella striata, Lima pectiniformis, Perna mytiloides, 

 Area quadrisulcata, Exogyra nana, Cidaris florigemma (spines). 



This quarry affords additional proof of the correctness of our 

 identification of the false-bedded rocks, d, of Pickering with the 

 Coral Rag, which is here found occupying the same position, with 

 beneath it some oolite (No. 4) of peculiar character, not seen in the 

 type section. The argillaceous portion of the Upper Calcareous Grit 

 is here seen to be much thinner. 



Our next illustrative section of these rocks is at Sinnington, about 

 3| miles west of Pickering, on the side of the Seven valley to which 

 we have already referred. 



Seven-valley Section, near Sinnington. 



On the east side of the valley, just behind the village, there is a 

 very extensive quarried surface, laying bare the structure of the 

 Corallian Series from the Upper Calcareous Grit to the very base of 

 the Middle Calcareous Grit, including, of course, the Trigonia-he&s. 

 A fault at the south end has thrown the Upper Calcareous Grit 

 against the Coral Rag and Coralline oolite, bringing all three classes 

 of rock into juxtaposition at a point where they can be easily 

 examined (see fig. 15). 



The two lower groups of this section, representing the Middle 

 Grit and the shelly cap (F) of the Lower Limestones, we have already 

 referred to ; the remainder serves to confirm the Pickering section, 

 with which all its beds agree, with the exception of a fine develop- 

 ment of Coral Rag. As all the other groups of that section are in 

 their places except group d, or the top stone, it is evident, as pre- 

 viously pointed out, that this peculiar false-bedded series represents 

 at Pickering, in position, if in no other way, the true Florigemrna- 

 Rag. The persistence of group e, or the " black posts " (D. a of 

 this section), seen here as well as at Pickering and near Hagg House, 

 and of which there is not a trace in the Scarborough district, is also 

 remarkable. The base-bed of this group, called by the workmen at 

 Pickering " hilly and holey," is the " cave line " throughout this dis- 

 trict. 



On this line occurs the celebrated Kirkdale Cave, in a quarry by 

 the side of the old road between Kirkby Moorside and Helmsle}^, 

 just above the ford across Hodge beck. It is well known that most 

 of the rivers hereabouts " swallow," i. e. run underground at certain 

 points, as their predecessors seem to have done at a higher level, of 

 which this cave now presents an example. The explanation is that 

 such beds present a hummocky surface of hard impure limestone diffi- 

 cult of solution, with interspaces filled in by a soft limestone brash, 

 which is readily disintegrated both chemically and mechanically by 

 the action of running water. The origin of the peculiar rock 

 called " black posts," as also of " throstler," though in some way 



