SUMMARY PLATE XI. 
This and the following two Plates, XII. and XIII., have been prepared from various sources, 
as well as from specimens already figured in the preceding plates, in order to illustrate the 
association of forms in all the series described in this Memoir. The sequence in each series is 
accurate, with certain exceptions, where it has been found necessary to alter to some extent the 
exact order of the species. These alterations have been noted below, and most of the forms 
necessarily omitted in this summary may be traced by comparing the plates with Table IV., 
“ Genealogy of the Arietidz in the Province of Central Europe.” ‘The species of the Medi- 
terranean Province figured in these plates, and not mentioned in that table, have been more 
or less noted or described in the chapter on “Descriptions of Genera and Species,” and are 
Fig. 7-13 and Fig. 17-19 on Plate XI., and Fig. 10 on Plate XIII. The remainder all occur in 
the Jurassic Province of Central Europe. 
The connecting bars designate affinity, and show the genesis of the forms. No attention 
has been paid to the geological horizons, but representative forms, or, as they have been called in 
the text, morphological equivalents, have been placed on the same, or nearly the same, horizon- 
tal lines in the three plates. ‘This has brought out very completely the curious discordance 
which occurs in the normal progressive series in the centre of the Arietide, as given on the 
right of Plate XI. and the whole of Plate XII. in the genera Caloceras, Vermiceras, Arnioceras, 
and Coroniceras. heir quadragonal whorls, and deep channels and keels in adults, and the 
absence of involute forms, are in marked contrast with Schlotheimia, Weehneroceras, and the more 
involute forms of Psiloceras, on the left of Plate XI., and the geratologous series at the other 
extreme of the group, Asteroceras, Agassiceras, and Oxynoticeras, as illustrated on Plate XIII. 
Psil. planorbe, var. leve, Fig. 1; var. plicata, Fig, 2. 
Psil. aphanoptychum (sp. Wah.), Fig. 11. 
Psil. Kammerkarense (sp. Wih.), Fig. 12, shows the more involute and plicated form. 
Psil. mesogenos (sp. Wih.), Fig. 13, is an involute shell really belonging to the true 
Levis stock, and therefore somewhat out of place at the top of the direct descendants of var. 
plicatus, but it is placed there for comparison with its morphological equivalents in other series. 
Weeh. curviornatum (sp. Wih.), Fig. 7, has the pile on the abdomen, a trifle too strongly 
shaded; but this form is undoubtedly distinct from Schlot. angulata. 
Weh. haploptychum (sp. Wih.), Fig. 8, is one of the typical forms of this genus, and 
the contrast between this and Schlot. angulata is well shown, 
Weh. toxophorum (sp. Wih.), Fig. 9, is a degenerate shell, having compressed whorls, 
and pile crossing the abdomen, as in the proximate radical Weh. curviornatum. It is, however, 
more involute. 
Weh. Emmerichi (sp. Wah.), Fig. 10, shows a notably involute shell, with degenerate 
pile and compressed whorls. 
Schlot. catenata, Fig. 3, gives the tongue-shaped connections between the pile on the 
abdomen, but they are somewhat too strongly shaded. 
Schlot. angulata, Fig. 4, is evidently a transition to the next species, 
Schlot. Charmassei, Fig. 5. The whorl is more involute, but the degenerate characters 
of compression in the whorls and-shallowing of the abdominal channel begin to appear. 
Schlot. Boucaultiana, Fig. 6. The involution has attained its maximum, and the degen- 
eration of the pile and channel is well marked. 
Cal. tortile, Fig. 14. The young in the centre of the umbilicus shows the close relationship 
to Psil. planorbe, var. plicata, below. 
Cal. carusense, lig. 15, has similar smooth young to that of-tortile below, and has no 
keel in the nealogic stage. 
Cal. Nodotianum, Fig. 16, is very similar to carusense, but with more compressed whorls 
and better developed pile. 
Cal. cycloides (sp. Wih.), Fig. 17, shows compressed degenerate whorls. 
Cal. Castagnolai (sp. Wih.), Fig. 18, is more degenerate than the last, but slightly 
more involute. 
Cal. abnormilobatum (sp. Wah.), Fig. 19, is a dwarfish and more degenerate form than 
Castagnolai, but has more involute whorls. 
Cal. suleatum, Hyatt, Fig. 20, shows smooth young, as in Fig. 15, and the growth of the 
pile from tubercles on the edge of the abdomen in the young. 
_ _Cal. Deffneri, Fig. 21, has the pile and tubercles too heavy, but it shows that the young 
is similar to that of Cad. sulcatum below, and that the pile have no abdominal extensions. 
Cal. laqueum, Fig. 22, is an extreme form of this species, which approximates very closely 
to a true spiratissimum, differing however in the sutures and in the age at which the keel 
appeared. This figure is therefore placed to the right, and under Verm. spiratissimum. The 
less specialized varieties of this species, which would have stood between Cad. tortile and Cal. 
carusense, have not been figured. 
_. Verm. spiratissimum, Fig. 23, shows typical form, with keel developed early, and but 
slight channels. : 
Verm. Conybeari, Fig. 24, shows normal untuberculated variety, with stout whorls and 
deep channels. 
Verm. ophioides, Fig. 25, exhibits the tuberculated pile and concentrated development 
of this species, as shown in the early age at which the tubercles appeared. 
