OF CONCHOLOGY. 211 



The other form of teeth among the uncini prevails on the bal- 

 ance of the lingual membrane. The same long, pj^. 4 

 broad plate is present, with its truncated upper 

 edge, but its base is more produced and is 

 widely rounded at the corners. The lance-like 

 projection of the centrals and laterals, and the 

 mitten-like process of the first three uncini, are 

 entirely wanting. There is, indeed, a thumb- 

 like projection on the side, but this bears no 

 resemblance to that of the first three laterals ; 

 it is on the outer instead of inner side of the -'^cli='^tina vngmea. 

 tooth, and is not a projecting point to the tooth. It is between 

 the upper edge of attachment and the cusp, and is rather a 

 spur thrown off from the last named process. This cusp is 

 present in all the uncini except the first three. It is placed on 

 the lower third of the tooth, from which it rises diagonally, ex- 

 panding at the sides in keeping with the expansion of the plate, 

 beyond which it projects considerably. It extends across the 

 whole breadtb of the tooth, and is best described as gouge- 

 shaped. The spur mentioned above is somewhat spoon-shaped. 



AH the plates on the membrane are well defined and distinctly 

 separated. 



Figure 3 gives the lower portion of one central, of the two 

 adjoining laterals, and two of the first three uncini. Figure 4 

 gives one of the balance of the uncini, with sufiicient portions of 

 the adjoining ones to show their diagonal arrangement on the 

 membrane. It is of great interest to compare with this mem- 

 brane that of the allied species Aohatina fasciata, which is given 

 below. A recent opportunity of examining the lingual mem- 

 brane of A. fasciata, shows that in that species there is great 

 uniformity in all the teeth, the centrals and first three laterals 

 do not in any way resemble those of A. virginea. 



Figs. 3 and 4 are drawn from photographs taken directly from 

 the microscope by our friend Mr. Sam. Powel. We have already 

 (Land & Freshwater Shells, Part I., 312, fig. 364), figured the 

 jaw of Achatina virginea. It is slightly arched, is attenuated 

 at the ends. It is composed of separate plates, fourteen in 

 the only specimen we have examined. 



Achatina fasciata, MUll, (PI. 9, fig. 6.) 



A specimen received from Cuba furnished the lingual mem- 

 brane here described. 



Teeth about 69 — 1 — 69 in each row. Transverse rows ar- 

 ranged en chevron. Teeth almost uniform, the centrals hardly 

 differing from the laterals except in being symmetrical, and in 



