60 On the Dentition o/Pella Bumupi. 



EXPLANATION OF PLATE IV. 



Fig. 1 . Macroehlamyi angulata. 



Figs. 2-2 h. Trochonanina bongaoensis. 



Figs. 3,3 a, Helix (Tlect(>tropis) squamulifera. 



Figs. 4, 4fl. (Chloritis) sifnduensis. 



Fig. 5. Cochloslyla (C'orasia) cBgrota, var. 



Figs. 6,6 a. Helicina contei'niina. 

 Fig. 7. Cydotus siihtamis. 



Figs. 8, 8 a. bongaoensis. 



Figs. 9, 9 a. AmpMdromus macidiferus. 

 Figs. 10, ] a. Lagochihis quinqueliratits. 

 Figs.W, 11a. Diplommatina Roebeleni. 



V. — On the Dentition o/Pella Burnupi, Mehill and 

 Ponsonhy. By Henry Suter, Christcluirch, New Zealand. 



[Plate V. B.] 



Some time ago Mr. J. H. Ponsonby kindly sent me a number 

 of Helicidse from South Africa, and, on carefully examining 

 tliem, I was astonished liow some of them showed distinct 

 relations to forms from New Zealand. Fortunately there was 

 one specimen of Pella Burnupi^ M. & P., in which the dried- 

 up animal was left, and, after proper treatment, I succeeded in 

 getting it out of the shell, leaving the tail well preserved. 

 In preparing jaw and radula great care was used, as those 

 parts of the mouth are often exceedingly fragile when the 

 animal has been dry for a long time. The mounting of the 

 radula was successful, but the jaw broke in several pieces, 

 without, however, impeding the study of its detail structure. 



Jaio (PI. V. B. fig. 1) arcuate, folded in about twcnt}- 

 vertical plaits, which are about five times longer than broad, 

 and strongly transversely striated. Between the plaits a 

 small transparent interstice is left. Cuttiug-margiu broadly 

 indented. 



Radula (fig. 2) tongue-shaped, consisting of numerous 

 transverse straight rows of teeth, 20 — 1 — 20, of which five or 

 six may be taken as laterals. 



Central tooth quadrangular, slightly longer than broad, 

 rounded in front ; reflexion tricuspid, the median cusp 

 reaching almost to the posterior end of the base ; the side 

 cusps short, sinuated at the outer sides; median cutting-point 

 well developed, extending a little over tlie next row of teeth ; 

 the side cutting-points minute. 



Laterals very much like the rhachidian, the median aud 



