DUMORTIERIA SUBUNDULATA. 
261 
of PI. XLIV, figs. 10 — 12, as Ditm. suhundulata var., is correctly placed with 
the present species, because it is so much more involute. Still it has the coarse 
ribs in the inner whorls changing to finer ribs ; and involution may be only a sign 
of progress. 
This specimen has no inconsiderable resemblance to Gramm. subcomptum 
(PI. XXX, figs. 11—14). In fact, Dr. Haug, to whom I sent a proof of PI. XLIV, 
wrote to me that this specimen " is Harp, subcomptum, Branco ; I do not think 
that it can be a Dumortieria, the ventral area is too acute, the ribs are too much 
waved, and the suture-line does not show the lateral saddle characteristic of the 
genus. Why should it not be a Gi-ammoceras I am much indebted to my 
friend for his critical remarks ; and I have quoted them here because they are 
worthy of every consideration. Still, a strict examination of the original specimen 
confirms me in my opinion that it is a Dumortieria ; and I rely on the coarse, 
distant ribs of the inner whorls,^ and the short, but quite complete, ventral pro- 
jection of the mouth as features which not only separate this specimen from 
Gramm. sulcomptum, but show that it is reaUy a Dumortieria. The difference in the 
length of the ventral projection between Gh^amm. subcomptum and this specimen is 
very striking, as a comparison of PI. XXX, fig. 14 with PI. XLIV, fig. 11 will 
demonstrate. 
Another specimen about which I feel some uncertainty is shown in PI. XLIII, 
figs. 8 — 10. At first I thought that this was a new species ; but I cannot say 
that it difi'ers from Dum. suhundulata in any way except being much larger. Its 
ventral area (fig, 9) appears more rounded than is the case, on account of absence 
of test not being quite correctly delineated ; but a somewhat rounded ventral area 
would not preclude it being a large form of the typical Dum. suhundulata, because 
such a ventral area would probably be the necessary concomitant of advanced age. 
There is then really no point in which this specimen difiers from Dum. subuudulata, 
except size ; and I consequently imagine it an unusually large variety of the species. 
It is possible that difference in locality might account for the diS*erence in size 
between this specimen and the examples figured in PI. XLV. The one came from 
the south of the Mendips, and the others from the Cotteswold district. The latter 
may, therefore, be a dwarf race or variety, or the former may be unusually large 
owing to more favourable circumstances. 
There can be little doubt of the descent of the large variety of Dum. suh- 
undulata, PI, XLIII, figs, 8 — 10, from Dum. Levesquei, PL XXXVII, figs, 6 — 8 ; 
and both specimens came from the same locality. The former shows the usual 
changes, namely, greater compression, broader whorls, and reduction of ribbing. 
If this be correct as regards its descent, then the Cotteswold forms of Dum. suh- 
undulata ought to be derived from the same species, otherwise the south-country 
^ The ribs are single, not fasciated as in Qramm. suhcomptmn. 
