BELLEROPHON. 
325 
seems so nearly to approach the Enghsh shell in general shape and in ornament 
that I think it must be regarded as identical. It has a very expanded mouth, of 
which there is no evidence in the British specimens. Its umbilicus is very variable 
in size, being sometimes slight but sometimes much larger than in the latter, and 
in perfect specimens it is closed by the expansion of the sides of the mouth. 
Barrois' figure^ of B. Pelops from the French Devonian comes very near our shells, 
and shows no expansion of the mouth, but has a very large umbilicus. Barrois 
notes its similarity to B. lineatus, Sandberger, and, if his identification of his shell 
with the American form is correct, it strengthens the probability of the identity of 
the latter with deFerussac's species. 
B. affinis, de Kon., and B. Meeki, de Kon., seem to be so similar that I have been 
unable to discover any line of distinction. De Koninck's figures are not, however^ 
very clearly individualised. 
Affinities. — B. tenuifascia, Sowerby,^ seems very like some of our more worn 
specimens and has a similar umbilicus, but it is distinguished, according to 
d'Orbigny,^ and as seen in Sowerby's type-specimen in the British Museum, by 
having an essentially linear, though prominent, keel. 
B. Munsteri, d'Orbigny,* has numerous very fine striae and its umbilicus is closed. 
B. imhricatus, Goldfuss,^ is not umbilicated. 
B. hiulcus, Martin sp.,^ seems very similar. Its possession of side ridges to the 
keel, by which d'Orbigny''^ distinguishes it, is of no value, as they are equally seen 
in B. striatus. However, judging from his figures, its keel is generally much 
broader and more coarsely marked. In one figure, on the other hand, it is very 
fine and narrow, and I can see nothing to distinguish that specimen from the 
present species. The specimen figured by Sowerby, however, shows that it is 
distinguished by its keel not being elevated above the rest of the shell, and by 
the greater rapidity of increase in its whorls. 
B. costatus, Sow.,^ has a sharper narrower keel of a different character, and 
some signs of spiral ornament. It also, as seen by de Koninck's figures,^ seems to 
increase more rapidly. 
1 1889, Barrois, 'Faun. Calc. d'Ebray,' p. 210, pi. xv, figs. 14 «, b. 
2 1824, Sowerby, ' Min. Conch.,' vol. v, p. 109, pi. cdlxx, figs. 2, 3. 
3 1840, de Ferussac and d'Orbigny, ' Hist. Nat. Ceph.,' p. 201, (Bellerophon) pi. i, figs. 6 and 7, 
and pi. V, figs. 14 — 18. 
* Ibid., p. 187, pi. ii, figs. 11—15. 
5 Ibid., p. 195, pi. V, figs. 1—4. 
6 1809, Martin, ' Petr. Derb.,' p. 15, pi. xl, fig. 1. 
7 1840, de Ferussac and d'Orbigny, ' Hist. Nat. Ceph.,' p. 196, (Bellerophon) pi. i, fig. 4 ; pi. iv, 
fig. 13 ; pi. V, figs. 5—8. 
8 1824, Sow., 'Min. Conch.,' vol. v, p. 110, pi. cdlxx, fig. 5, and 1840, de F6r. and d'Orb., 
'Hist. Nat. Ceph.,' p. 198, (BeUerophon) pi. i, figs. 2, 3, 5 ; pi. v, figs. 9-13; pi. vi, figs. 3—5. 
9 1883, de Koninck, ' Ann. Mus. Eoy. H. N. Belg.,' vol. viii, pt. 4, p. 135, pi. xl, figs. 1—3. 
