132 PROCEEDINGS OF THE ACADEMY OF [Feb., 



Pleurodonte (Eurycratera) jamaioensis Gmel. Plate VII. 



Good series of this species were obtained from Somerset, Ridge near 

 Lincoln and Garrett's woods, and a few specimens from Benmore 

 woods, Bloomfield, Cedar Hill woods, and the woods at King Edward 

 Hotel. While these vary considerably in size, the same general form 

 is preserved, so that from the smallest to the largest specimens the 

 dimensions show a nearly even gradation. On account of the shape 

 of the shell, comparable measurements could only be obtained with 

 any approach to accuracy by making certain conventions in regard 

 to the position in which the height and width should be measured. 

 The "height" is measured from the apex of the shell to the outer edge 

 of the lip, the greatest obtainable measurement being taken; the 

 width is measured from just above the upper angle of the lip to the 

 opposite whorl, the measurement being taken whorl to whorl. The 

 height so obtained is not far different from that measured parallel 

 to the axis, but is, of course, much more exact. The height of the 

 mouth was also measured from the same angle of the lip to the tangent- 

 point on the portion of the lip opposite and was found to range near 

 the diameter of the shell. This species is still living at the first four 

 localities mentioned, but, from the appearance of the shells collected, 

 it is most likely extinct at the Bloomfield, Cedar Hill and King Edward 

 Hotel woods. The specimens from Garrett's woods ran uniformly 

 smaller than those from the other locations; of 28 adult shells but 

 3 exceed 38 x 49 mm. and but one shell of this species from all other 

 localities is as small as this, and that one is an injured shell from the 

 Benmore woods which was stunted by the injury. Of the 28 shells 

 from Garrett's woods mentioned, 18, or 64 per cent., ranged between 

 35 x 45 mm. and 37 x 47 mm. ; but one fell below 35 x 45 mm. and 

 only three were above 38 x 49 mm. The largest shell from this locality 

 was 39 x 52 mm. The index or ratio of width to height ranges from 

 .735 to .82, with 75 per cent, of the shells between .77 and .79. Of 

 the other large series, the Ridge near Lincoln colony and the Somerset 

 group are nearly of the same size, ranging from 40 x 51 mm. to 45 x 57 

 mm., with the exception of one small specimen from Somerset which 

 was evidently abnormally small, due to some irregularity in growth, 

 as was indicated by the growth lines. 



The Somerset colonies furnished shells of more uniform index or 

 ratio of width to height than those of the Ridge near Lincoln colony ; 

 this index ranges from .76 to .815, but of the 30 specimens measured 

 from the Somerset locality only 3 fall below .77 and only 6 are above 

 .80. Of the other 21 (or 70 per cent.) which range from .77 to .80, 



