144 MOLLUSCA FROM THE CRAG. 



Longest diameter, \\ inch. 



Locality. Cor. Crag, Ramsholt. 

 Red Crag, Sutton. 



This is not a very abundant shell in my cabinet from either formation. It appears 

 to be quite distinct from N. hemiclausa, and agrees in most of its characters with 

 N. varians, from Touraine. In this shell the umbilicus is tolerably large and deep, with 

 a very slight ridge at the lower part, which is perceptible in some of the specimens 

 from Touraine, lent me for comparison by Mr. Lyell. The shell figured by M. Nyst is 

 probably a variety of this, but the volutions of my specimens are more depressed ; 

 the left lip is callous, particularly at the upper angle of the aperture, and it 

 never covers the umbilicus. A slight flattening is visible on the left side, but 

 apparently not deep enough for the pressure of a calcareous operculum, nor is there 

 any mark within the outer lip. This shell is striated beneath the outer coating. It 

 somewhat resembles in form N. plumbea, Lamarck, but it is a thicker shell, more 

 elongated, and has a more distinct and elevated spire. 



6. Natica hemiclausa. /. Soiv. Tab. XIV, fig. 5, a — b. 



Natica hemiclausa. J. Sow. Min. Conch, t. 479, fig. 2, 1824. 



— S. Wood. Catalogue 1842. 



— Morris. Catalogue of Brit. Fossils, p. 153, 1843. 



N. Testa ovato-conicd, ohiiqud, laoigatd, politd ; spird comided ; anfractibus se,v 

 depressis ; aperturd ovatd ; labio callosb ; umbilico tecto. 



Shell ovato-conical, oblique, smf)Oth, and polished ; spire conical ; whorls sLx, 

 depressed ; aperture ovate, with a callous left lip closing the umbilicus. 



Long, diameter, 1 inch. 



Locality. Red Crag, Walton Naze and Sutton. 



This is also an abundant shell. The umbilicus is quite covered when the animal 

 has reached maturity. The specimen figured in ' Min. Conch.' was a young individual. 

 It much resembles N. mammilla, Lamarck, but its left lip is less callous, especially 

 at the upper part, and it has a rather more prominent spire ; it was smooth and 

 glossy, and, like N. mammilla, has the volutions equally depressed. It also shows a 

 deepened suture when the outer covering has been removed, a condition in which the 

 Crag Naticae are often found. M. Philippi considered this, in his first vol. p. 162, to be 

 the same species as N. Guillemini, Payr., and, in vol. ii, p. 140, he has identified it 

 (doubtfully) with N. macilenta (t. 24, f. 14). I think, however, the Crag shell 

 sufiiciently distinct from either. Specimens are occasionally more elongate than the 

 one represented. 



