HA SWELL — ON THE DENUDATION OF ARTHUR'S SEAT. 



93 



lines of growth. In a young state the shell is longitudinally ribbed, the ribs being 

 tumid and close together ; no trace of this is seeu in the adult. 



A second specimen, probably of the same species, is rather larger, 

 and has a rib between the suture and the marginal angle, and six 

 primary ribs on the body-whorl. 



Both these examples are distorted by pressure. The smaller ex- 

 ample (figured) is compressed laterally. The rock is a very hard 

 chalk, much resembling some of the lighter-coloured clay concretions ; 

 fossils are yellowish. 



(?) Fusus. 



This form differs from the Brighton specimens chiefly in the large number of equal- 

 sized ribs, a character to which little importance can be given; it may be varietal, but 

 more probably is but an adult ornament, just as are the longitudinal ribs, a feature pecu- 

 liar to the young. The lip is a little inflected. The space between the posterior two 

 ribs appears to have supported a sharp projecting keel, now broken away. 



Solarium Binghami (Baily). 



Shell thick, much depressed, not half so high as wide ; composed of about six whorls, 

 which very gradually increase in size. The upper side of the shell is a greatly depressed 

 cone ; the under side a large conical hollow. The whorls are five-angular ; they are 

 attached by one side, two converge interiorly to form the base, one perpendicular forms 

 the side of the shell, and the fifth forms the slightly oblique upper surface. 



This last form of the upper surface of the whorl is ornamented mar- 

 ginally by upwards of forty tubercles, which are elongated in a 

 direction at right angles with the line of growth. A second row, 

 more numerous and much smaller, passes round near to the suture. 

 Both the interspace and tubercles are finely striated spirally. The 

 perpendicular side is not more than half the width of the outer basal 

 space ; it has on its lower margin a row of tubercles similar to that 

 on its upper margin, but they are narrower and half as numerous 

 again. The tubercles so entirely occupy the side that the groove 

 between the two rows is not half so wide as either of them. The 

 outer part of the base is very finely cancellated; the angle it makes 

 with the inner half is nodulated with seventeen large tubercles. 

 The inferior suture is much more impressed than the superior one, 

 and the sufcural margin of the base is ornamented with a row of 

 tubercles, about as numerous as that on the upper margin of the 

 side. The umbilicus is nearly as deep as wide. 



ON THE DENUDATION OF AETHUH'S SEAT. 

 Br James Haswell, M.A. 



" Quid magis est saxo durum ? quid mollius unda ? 

 Dura tamen molli saxa cavantur aqua." 



The condition of Central Scotland during the long period repre- 



