SUMMARY PLATE XL 



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 Arietidae 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 XL, 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. Xo 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 Arietidae, as given on the 

 right of Plate XL and the whole of Plate XII. in the genera Caloceras, Vermiceras, Arnioceras, 

 and Coroniceras. Their quadragonal whorls, and deep channels and keels in adults, and the 

 absence of involute forms, are in marked contrast with Schlotheimia, Waehneroceras, and the more 

 involute forms of Psiloceras, on the left of Plate XL, 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. Wah.), Fig. 12, shows the more involute and plicated form. 



Psil. mesogenos (sp. Wah.), Fig. 13, is an involute shell really belonging to the true 

 Li \ is 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. 



Wseh. curviornatum (sp. Wiih. |, Fig. 7, has the pilae on the abdomen, a trifle too strongly 

 shaded; but this form is undoubtedly distinct from Schlot. angulata. 



Waeh. haploptychum (sp. Wiih.), Fig. S, is one of the typical forms of this genus, and 

 the contrast between this and Schlot. angulata is well shown. 



Waeh. toxophorum (sp. Wiih.), Fig. 9, is a degenerate shell, having compressed whorls, 

 and pilae crossing the abdomen, as iu the proximate radical Waeh. curviornatum. It is, however, 

 more involute. 



Waeh. Emmerichi (sp. Wah.), Fig. 10, shows a notably involute shell, with degenerate 

 pilse and compressed whorls. 



Schlot. catenata, Fig. 3, gives the tongue-shaped connections between the pilae 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 pike 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, Fig. 15, has similar smooth young to that of tortile below, and has no 

 keel in the nealogic stage. 



Cal. Nodotiarrum, Fig. 16, is very similar to carusense, but with more compressed whorls 

 and better developed pilae. 



Cal. cycloides (sp. Wiih.), Fig. 17, shows compressed degenerate whorls. 



Cal. Castagnolai (sp. Wah.), Fig. 18, is more degenerate than the last, but slightly 

 more involute. 



Cal. abnormilobatum (sp. Wiih.), Fig. 19, is a dwarfish and more degenerate form than 

 Castagnolai, but has more involute w r horls. 



Cal. sulcatum. Hyatt, Fig. 20, shows smooth young, as in Fig. 15, and the growth of the 

 pilae from tubercles on the edge of the abdomen in the young. 



_ Cal. Deffneri, Fig. 21, has the pilae and tubercles too heavy, but it shows that the young 

 is similar to that of Cal. sulcatum below, ami that the pilae 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 Cal. 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 tubereulated pilae and concentrated development 

 of this species, as shown in tin- curly age at which the tubercles appeared. 



