370 INFERIOR OOLITE AMMONITES. 
once negatived by the septation; for in Sonn. nodata the superior lateral lobe 
has lost its bilateral symmetry; in Sonn. spinosa the symmetry is maintained. 
In whorl-shape Sonn. nodata is like Sonn. crassispinata, but it is much less 
spinous, and differs in septation. The combination of round whorls, small spines, 
and reclinate ribs separates it from any other species. 
The type-specimen of this species, an almost wholly-septate example, is shown 
in Pl. LXXXIX—side view, fig. 1; front view in outline, fig. 2; and parts of two 
suture-lines, fig. 3. In the same plate a young shell has been drawn—side view, 
fig. 4, and front view, fig. 5. It may be remarked that this young shell does not 
agree exactly with the inner whorls of the type, because it has rather smaller 
spines. It can scarcely, therefore, be considered as the actual young of the 
type nodata, though it is sufficiently close to give a good idea of what the young 
shell would be. Strictly speaking, it is, no doubt, the young of a species which 
joins nodata to paucinodata, a form of which I have not yet obtained an older 
example. It has a likeness to Sonn. subspinosa (Pl. LXXXIV, figs. 4, 5), but may 
be at once separated therefrom because of the difference in ribbing on the area 
between the spines and the carina. In this form bifurcation is rare; in Sonn. 
subspinosa trifurcation is common. 
SonniniaA pavoinopata, S. Buckman. Plate XCI, figs. 7—9. 
Discoidal, compressed, carinate. Whorls ornamented with small, subundulate, 
direct, upright, ventrally-obsolete coste. (The spinous stage ends at about 
35 mm. diameter). Ventral area arched, divided by a _ small, indistinct, 
ill-defined carina; core carinate. Inner margin rather ill-defined, subconvex, fairly 
sloped. Inclusion about one-half. Umbilicus excentric, graduate, costate, 
centrally spinous. Whorl-section oblong, about one-fifth indented. Suture-line 
with an asymmetrical superior lateral lobe, the lateral lobules not opposite, the 
terminal lobule intra-axial, anisosceloid, and inequicellate. 
This species has externally some resemblance to Sonn. quadrifida; and the 
reduced size at which the forms have been depicted in the plate has given a false 
impression, by considerably heightening this likeness. However, Sonn. paucinodata 
is less carinate, less spmous, on the whole more costate, slightly thinner, and 
certainly less marginate than Sonn. quadrifida. Internally the septa are very 
different (see page 369). Septation, again, distinguishes this species from Sonn. 
papilionacea, while, externally, the more marked costation of the early costate stage 
is a sufficient distinction. 
The upright ribs, or the excentric umbilicus, or the longer duration of a pro- 
