BELLEROPHON. 
323 
plicated by finer ones whicb tend to arrange themselves in groups. Mouth not 
preserved in the English specimens, but showing a callosity on its inner sides. 
Size. — About 18 mm. in height; 20 mm. in width. 
Localities. — There are four specimens from Lummaton in my Collection, three 
others probably from the same locality in the Torquay Museum, one from Barton 
and four from Wolborough in the Museum of Practical Geology, and one from 
Chudleigh in Mr. Vicary's Collection. ' - 
Remarks. — This species seems to be liable to very considerable variation both 
in shape and in ornament. Generally speaking it appears very globose, but the 
specimens figured by Phillips and some others are decidedly broader and flatter. 
The ornamentation is very definite on some of our specimens, but in others it is 
much more indistinct, and seems somewhat changed in character, the striee being 
more numerous, oblique, close, and arranged in groups, and the keel seeming 
smaller and more rounded. I was at first inclined to regard these points as 
indicating a specific distinction, but further examination leads me to believe that 
they are partly due to crushing and deterioration during fossilization, and partly 
to individual variation. Thus, even in the most typical specimens with clear cut 
distant striae, signs of other indistinct lines may be observed under a lens ; and in 
other specimens the development of these secondary lines may be traced until 
they are seen to become similar to the original strise. Moreover in some specimens 
these original strise are considerably 'coarser and more distant than in others. 
While in the main the strise are uniform, there are some slight indications of inequali- 
ties which might indicate a tendency to undi^lations in an older stage of growth 
than that of any of our specimens, so that then they might assume quite a different 
appearance, such as is seen in some foreign examples of de Ferussac's species. 
Although I have not been able to find the original of Phillips' figure, there can 
be no doubt of the identity of our specimens with the species described by him. 
Whether it is identical with de Ferussac's original species is a larger question. It has 
been separated from it by d'Archiac and de Verneuil,^ but these authorities assign 
no reasons for their view. The only point of difference which I have been able to 
discover is that the English specimens have a somewhat more distinct and larger 
umbilicus extending sometimes almost to a quarter the width of the shell. This 
is in every case filled with matrix, but there is every reason to suppose that it was 
definite, perforate, and deep. De Ferussac and d'Orbigny describe it as slight, and 
their figures seem to represent it as small, and with less defined margins than is seen 
in our specimens. Sandberger, who gives figures of several varieties varying much 
both in the size of the umbilicus and in the fineness of the strias, is almost the only 
foreign author who figures B. striatus with as large an umbilicus, though F. A. 
Romer's figure shows that one existed. In our shells, however, the mouth is in 
1 1842, d'Archiac and de Verneuil, ' Geol. Trans.,' ser. 2, vol. vi, pt. 2, p. 353. 
42 
