189. _Genealogical Tree of the Botryodea._--The peculiar order #Botryodea# (p. 1103), which is both difficult to investigate and insufficiently known, presents great phylogenetic difficulties both as to its ascent and descent. Probably the different genera of this order have been polyphyletically developed from different groups of #Cyrtoidea# (perhaps also to some extent of #Spyroidea#) by the formation of lobes in the cephalis. The three families of #Botryodea# are related to each other in the same way as are the three first families of the #Cyrtoidea#. From the single-jointed Cannobotryida (corresponding to the Monocyrtida), the two-jointed Lithobotryida (corresponding to the Dicyrtida), may be derived by the development of a basal thorax, and from the latter the three-jointed Pylobotryida (like the Tricyrtida) by the addition of an abdomen. In the last two families the forms with an open basal mouth {cxxii}(Botryopylida and Botryocyrtida) are to be regarded as primitive: the Botryocellida and Botryocampida have arisen by the closure of this mouth with a basal lattice-plate. 190. _Genealogical Tree of the Cyrtoidea._--The multiform and extensive group #Cyrtoidea# presents the greatest difficulties to be found in the phylogeny of the NASSELLARIA, because their morphological relations are most complicated, and because similar forms very often appear to be of quite different origin. The great majority of the #Cyrtoidea# show more or less clearly a combination of the three structural elements: sagittal ring, basal tripod, and latticed cephalis (p. 891). There are also, however, numerous #Cyrtoidea#, whose skeleton no longer shows any trace of the sagittal ring. Many of these show as the basis of the skeleton a strong basal tripod with an apical spine, around which the cephalis has obviously been secondarily developed, _e.g._, the remarkable Euscenida (p. 1146, Pls. 53, 97) and the interesting Callimitrida (p. 1217, Pls. 63, 64). These may have been derived immediately from the #Plectoidea# without any relation to the #Stephoidea#. There are also numerous true Monocyrtida, whose shell consists of a simple latticed cephalis without a trace of the sagittal ring or basal tripod (Cyrtocalpida, Pl. 51, figs. 9-13; Pl. 98, fig. 13); these may have been developed directly from the skeletonless Nassellida by the formation of a simple ovoid _Gromia_-like shell, and may have no relation either to the #Stephoidea# or #Plectoidea#. On these grounds, as well as from the complicated relationships of the many smaller groups of #Cyrtoidea#, it is probable that the whole order has been developed polyphyletically from different divisions of the #Plectellaria#.