GASTEROPODA. 55 



This shell may be considered to form only a section of Littorina, agreeing in the 

 general characters with the genus Pagodm of Gray, with which, probably, the discovery of 

 more perfect specimens may assimilate it. 



AMBKRLEYA (PAGODUS) NODOSA. Plate V, fig. 19. 



TEREBUA NODOSA, Buckman. 1845. Geol. of Cheltenham, p. 102. 



A. Testa turrild, ventricosd; spird elatd, apice acuto; anfractibus (6) infra nodulosis, 

 nodulis numerosis superne apud suturam cingulo nodulorum minorum ornatis; anfractu 

 ultimo basi costulis obscuris tribits cincto. 



Shell turreted, ventricose; spire elevated; apex acute; whorls (6) convex on their lower 

 portions, and nodulated ; the nodules closely arranged, and forming a small belt near to 

 the base of the whorl ; another, much smaller and indistinct, circle of nodules encompasses 

 the whorls upon their upper portions near to the suture ; the last whorl has at its base 

 three indistinct, narrow, encircling costae. 



The number of nodules gradually increases in each volution, the last whorl having 

 about 18 ; the last two volutions are very ventricose, which give to the spire a slightly 

 concave figure ; in the younger state, consequently, the figure is more slender than in the 

 adult. Our two specimens, which are of different stages of growth, present the following 

 proportions: Adult. Axis 24 lines, transverse diameter 15 lines, length of aperture 11 

 lines, breadth of aperture 8 lines. Young state. Axis 16 lines, transverse diameter 9 

 lines, length of aperture 6 lines, breadth 4 lines. 



Locality. It is very rare, the planking of Minchinhampton Common has furnished five 

 examples, and several imperfect casts have been obtained in the Stonesfield slate at another 

 place in the same vicinity : these casts have enabled us to ascertain the absence of a central 

 columella. 



Obs. The specimen submitted to the artist was rather imperfect at the base of the 

 aperture, which, together with the position, give it the aspect of a regular notch at that 

 part of the shell. 



Family NERITID.E. 



NERITA, Linn. 1758. 



Shell semiglobose ; spire short, sometimes not produced, consisting of few volutions ; 

 aperture large, semilunar; outer lip thick, inner lip thickened, usually flattened, and 

 striated or dentated at its inner edge. 



The fossil species of Nerita, from the Great Oolite, may be divided into the three 

 following sections, as dependent on the character of the inner lip : 



