144 MOLLUSCA FROM THE CRAG. 



Longest diameter, If 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 oper- 

 culum, 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. 



n 



6. Natica hemiclausa. J. Sow. Tab. SET, fig. 5, a — b. 



Natica hemiclausa. J. Sow. Min. Conch, t. 4/9, fig. 2, 1824. 



— S. Wood. Catalogue 1842. 



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



N. Testa ovato-conicd, obliqud, laevigata, politd; spird conoided; anfractibus sex 

 depressis ; aperturd ovatd ; labio calloso ; umbilico tecto. 



Shell ovato-conical, oblique, smooth, and polished ; spire conical ; whorls six, 

 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 condi- 

 tion in which the Crag Naticas 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 sufficiently distinct from either. Specimens are occa- 

 sionally more elongate than the one represented. 



