THE CORALLIAN ROCKS OF ENGLAND. 263 



due to the greater development of particular beds there than else- 

 where. 



Beginning at the base near Weymouth, we find that the series com- 

 mences with a considerable thickness (about 30 ft.) of calcareous 

 sand, with hard bands of grit. These are well exhibited beneath 

 the jNothe Fort at the end of Weymouth Pier, where the curious 

 interlacing bands, due probably to decayed fucoids, have long been 

 noticed. The whole has, however, undergone much alteration since 

 its original deposition, by the action of chemical and other agencies, 

 as is the case with similar beds in Yorkshire. 



The change into these beds from the Oxford Clay below is by no 

 means so gradual as it is in many other areas. Mr. Damon says 

 that " the junction at the Xothe, noAv no longer visible, is sharp 

 and well-defined ;" and certainly on the western side, in the Fleet, 

 it is remarkably so. The uppermost bed of clay there is surmounted 

 by a thick layer of Ostrea dilatata, associated with Ammonites cor- 

 datus, Ostrea gregaria, and Serjpula tricarinata, which is immediately 

 covered by the sands, with great abundance of Perna quadrata, a 

 very characteristic fossil of the beds throughout this district. In a 

 brickyard between these two localities the change at the base is also 

 sudden, though the overlying sands are more argillaceous and sup- 

 port abundance of Myacites and Pholadomycc. The beds of cal- 

 careous grit become more strongly developed at the top ; and the 

 uppermost one is somewhat ferruginous. In order to avoid any 

 undue assumption in the names used, we think it best to employ 

 local designations for each series of beds ; and this series we call the 

 " Xothe Grits." 



The fossils that have occurred to us in these beds near Weymouth 

 are the following : — 



Ammonites cordatus (Sow.). 

 Belemnites liastatus (Blainv.). 

 Cerithium muricatum (Sow.), var. 

 Chemnitzia, sp. 



Pleurotomaria Miinsteri (Sow.). 

 Opis Phillipsi (Mor.). 

 Cyprina tancrediiformis(.Z?Z. §■ H.). 

 Trigonia perlata (Ag.). 

 Myacites decurtatus (Ph.). 

 Pholadomya asqualis (Sow.). 



concinna (Ag.). 



Perna quadrata (Sow.). 



Pecten fibrosus (Sow.). 

 Avicula ovalis (Ph.). 

 Anomia radiata (Ph.). 

 Ostrea eulitaria (Sow.). 



gregaria (Sow.). 



— — dilatata (Sow.). 



, sp. (deltoid form). 



Exogyra spiralis (Gold/.). 

 Serpula sulcata (Sow.). 



tricarinata (Sow.). 



Millericrinus echinatus (Ph.). 



This is not an entirely distinct fauna from that of the Oxford 

 Clay below ; but there are some species, such as Trigonia perlata > 

 Pecten fibrosus, Avicula ovalis, and Millericrinus echinatus, which 

 are very characteristic forms and assist much in correlation. 



The development of the Nothe Grits on the northern side of the 

 anticlinal from Osmington to Abbotsbury shows, like most of the 

 series, a considerable diminution. At the former place their thick- 

 ness is only 12 feet, and their colour is darker. The fossils are 

 tolerably numerous, and remarkable for their large size, especially 

 the Trigonia perlata (both valves) and Ostrea dilatata, which are 

 immense. We note also, in addition to the forms met with at Wey- 



