152 



PROCEEDINGS OF THE ACADEMY OF 



[Feb., 



The irregularity shown in the frequency curve of heights in fig. 9 

 is no doubt due to the fact that but a small series was taken at this 

 station. 



Pleurodonte acuta goniasmos A. D. B. Plate XI, figs. 4, 6, 7. 



At the Benmore woods, Mandeville. 



Shell ovate conical, rather higher than the last, consisting of 4£ 

 to 5h whorls, of which the last has a distinctly angled periphery, but 

 is convex above and below and not excavated above the periphery, 

 as is commonly the case in the Kendal Road colony. They do not 

 include any very much depressed forms in the 42 specimens measured, 

 these run above .53 in index, with the exception of 10 specimens whose 

 indices range from .495 to .525; of the rest, 15 are above .575, and 8 



Fig. 12. — Benmore Woods. 



of these are above 60. The average index for the entire series is .56. 

 The heights vary considerably, but average about 21.5 mm., with an 

 average width of 38.4 mm. ; the mean divergence ranges from 120° to 

 110°. The highest index measured, .635, was in a shell of medium size, 

 of which the dimensions were 23.5 x 37 mm. 



The shells of this colony are prevailingly two-toothed, though the 

 outer tooth is the only one that is strongly developed, and in the 25 

 that show two teeth (59^ per cent.) the inner tooth is rather small in 

 most of the specimens. The other 17 specimens (40^ per cent.) only 

 show one tooth, with no trace of the second, inner one. The umbilicus 

 is normally closed, but is partly open in one specimen which is smaller 

 than the average, although it does not seem to be abnormal or injured 



