Fossil Remains on the Yorkshire Coast. 227 



with those of more complete specimens, the animal appears to have averaged 

 from fifteen to twenty feet in length. The large specimen in the Scarborough 

 museum would measure, if complete, at least eighteen feet. ]ts general 

 characters resemble those of the Plesiosaurus common in the lias of Dorset. 

 The Teleosaurus Chapmanni is sometimes found with the remains of the bony 

 plates or scales attached, as in the splendid Whitby specimen, and some 

 fragments in the Scarborough museum. It is rarely obtained with a perfect 

 snout, the dilated extremity* being generally broken off. 



Above the beds containing these remains, the large and beautiful A^autilus 

 astacoides and Ammonites HeterophijUus occur in argillaceous nodules. When 

 slit, they present beautifully the internal generic distinction, the chambers 

 being generally filled with calcareous spar, and the siphuncle with only lias 

 shale. The surrounding nodules, in some rare instances, are composed of 

 sulphuret of iron. In this portion of the series, large fragments of bitumi- 

 nized, coniferous wood are very common, having occasionally a thin coating 

 of jet. From thirty to sixty feet above these strata. Ammonites Walcotti and 

 A.ovatus occur, both in the shale and argillaceous nodules. 



At the Peak Hill, near the top of the upper alum shale, Trigonia literata 

 and Ammonites crassus are found in a thin layer. The latter is remarkable 

 for the thickness of its whorls, and the frequent decomposition of those which 

 constituted the centre of the shell. 



A little above these strata. Ammonites communis, and A. Jibulatus are 

 invariably found in small nodules, especially at the Peak to the south, and at 

 Hawsker, to the north of Robin Hood's Bay. At both places the upper 

 portion of the stratum is seen to great advantage as it descends to the Scar. 

 At the Peak, imperfect remains of an Astacus occur in the same layer of 

 nodules, but generally so crushed that its character is indeterminable. 



The top of this shale at the Peak Hill, appears to contain Ammonites striatu- 

 lus, enclosed in indurated calcareous masses ; and I am not aware of its having 

 been met with at any other locality. It occurs so near the top that doubts are 

 entertained whether it belongs to the alum shale, or to the overlying in- 

 ferior oolite. 



Inferior Oolite. 



The subdivisions of this formation next come under our notice. They are 

 best seen at Blue Wick, which presents the following ascending section : 



a. Thick beds of dark grey, finely grained sandstone 20 feet. 



b. Irregular beds of yellow sandstone 20 



* See Buckland's Bridgewater Treatise, PI. 5. 

 2 G 2 



