260 
INFERIOR OOLITE AMMONITES. 
fine stride of that species, while the umbilicus is much larger and the whorls are 
narrower. 
Bum. suhundulata has a very Grammoceratan aspect. Though its ribs are 
generally direct, which is the characteristic trait of Dumortieria, yet sometimes they 
have, especially on the body-chamber, a slight lateral bend. Its suture-line is 
also not quite characteristic ; because the length of the superior-lateral and 
siphonal lobes is much reduced, and the obliquity of the inner portion is not so 
apparent as in other species of the genus. 
The species of Grammoceras to which Dum. suhundulata bears the most like- 
ness is Gramm. distans, which, however, has its ribs rather more bent laterally 
and ventrally. 
When founding the species " Rarpoceras suhundulatum," Branco divided it into 
three varieties ; but I cannot consent to unite the forms he has figured. Three of 
his figures, comprising his " Varietdt externe-costatum" and " Varietal externe- 
comptum," belong to Dumortieria; but his " Varietdt externe-punctatum" is a 
Grammoceras. 
Dr. Haug^ in dealing with Branco's figures of " suhundulatum " noticed that 
*' Varietdt externe-punctatum " appeared to belong to the HarjJ. aalense-grouip. Of 
the others he made three varieties under the name " suhwidulata," for two of 
which he preserved Branco's names, ''Varietdt externe-costata" and ''Varietdt 
externe-comptai" and for the third adopted Quenstedt's name " striatulo-costata." 
My method of division differs from this, in that I have given Quenstedt's 
" striatulo-costata " specific rank, and have combined therewith Branco's " externe- 
costatum.^' Therefore I had divided Branco's "suhundulatum^^ into three 
species : — (1), the forms referred to Bum. striatulo-costata (see p. 243) ; (2), the 
present species ; (3), the form referred to Gramm. distans (p. 196). To any one 
of these three the name " suhundulatum^^ covldi have been applied; but I con- 
sidered it best to retain Quenstedt's name for 1 ; and in choosing whether 2 or 3 
should bear the name " suhundulatum " I followed Dr. Haug, in part, in applying 
it to 2. It was then necessary to give a new name only to 3. 
The type-figure of the present species must be the fig. 4 of Branco's pi. iii ; 
as his fig. 3 of the same plate, and fig. 1, pi. iv, have been removed from this 
association. Fig. 4 (pi. iii) shows the characters which I consider to mark the 
species, namely, e volute compressed whorls and coarse ribs. In the latter character, 
however, there may be modification ; and that is the reason why I have joined 
Branco's fig. 3 (pi. ii) as probably belonging to this species. The names exierne- 
costatum, externe-comptum, and externe-punctatum may be discarded as of no 
further use. 
I am not quite sure that a specimen which I have described in the explanation 
1 " Polymorphidae," ' Neues Jahrbucli fiir Miueralogie,' &c., Bd. ii, p. 13-i, 1S87. 
