144 
MONOGRAPH OF THE GENUS STROPHIA. 
DIMENSIONS. 
Size of type, .90 by .42. Largest specimen, 1.08 by .49 ; 
smallest, .95 by .37. Greatest diameter, .90 ; smallest .37. Longest 
specimen, 1.03 ; shortest, .85. 
OBSERVATIONS. 
Variation lies between a margin as thin as in typical S. grayi, 
sometimes protruded, frontal bar and all, and a thickened margin, with 
a very low frontal bar. 
As will be seen this sub-species, as well as S. g. gigantea, possesses 
some of the characters of both S. gray! and S. ritchiei but as the 
specimens which show intergrading links are between these two forms 
and 8. grayi, this fact, taken in connection w r ith the circumstances 
under which they are found, points clearly to the conclusion that they 
are derived directly from S. grayi. 
HABITS AND DISTRIBUTION, 
I found about fifty of this singular little Strophia clinging to the 
stems of tw 7 o or three small trees that grew just south of the deep 
gorge, that limits the southward range of S. grayi, as given under that 
species. The space in which they occurrred could not have exceeded a 
hundred square feet. No specimens of S. grayi, "were, however, found 
very near them, and this little colony had become isolated, and from 
some cause had advanced far toward forming a species. 
40 STROPHIA EBURNSA Novo, 
Ivory Strophia. 
Fig. 45, A, front view, B, side view of type. 
DESCRIPTION. 
Sp. Ch. Size rather small. Shell, quite thick. Striations, 
present. Whirls, ten. Examined, 100 specimens. 
Form of shell, an elongated cylinder "with the first three whirls 
about equal in diameter, the fourth is but little smaller, then the shell 
slopes to a rather acute point, forming an angle of sixty-five degrees. 
The striations are quite numerous, twenty-five to the first whirl, 
are not prominent, quite regular, but not arranged in lines. All are 
considerably inclined from right to left, they are smoothly rounded 
