Family LVIII. Pylobotryida, Haeckel (sensu emendato).
Pylobotryida, Haeckel, 1881, Prodromus, p. 440.
Definition.—Botryodea trithalamia, the shell of which is composed of a lobate cephalis, a thorax, and an abdomen.
The family Pylobotryida comprises those Botryodea in which the shell exhibits two parallel transverse annular constrictions, and is divided by these into three successive joints, corresponding to the cephalis, the thorax, and the abdomen of the Tricyrtida. As in the latter, the abdomen is here also a later production, arising from the terminal mouth of the thorax; therefore the Pylobotryida must be derived phylogenetically from the Lithobotryida.
Two genera of Pylobotryida were incompletely described in 1860 by Ehrenberg, Botryocyrtis and Botryocampe. We retain them here, with a stricter definition, however. Two other genera were added in my Prodromus—Pylobotrys and Phormobotrys. The small number of species here enumerated may be easily increased, since numerous forms, belonging probably to this family, are not sufficiently known. Their study is, however, very difficult and requires accurate examination of the tiny shells from different sides.
The four genera of Pylobotryida, here described, represent two different subfamilies. The terminal mouth of the abdomen remains open in the Botryocyrtida, whilst it becomes closed by a lattice-plate in the Botryocampida. There are in both groups shells with and without porous tubes; the number of these tubes, and also the number and disposition of the lobes in the cephalis, exhibits remarkable differences in the different species of those genera, and may in future serve for their division into a greater number of genera.
Synopsis of the Genera of Pylobotryida.
I. Subfamily Botryocyrtida. Mouth of the abdomen open. |  | Cephalis without porous tubes, | 492. Botryocyrtis. |
| Cephalis with a variable number of porous tubes, | 493. Pylobotrys. | ||
II. Subfamily Botryocampida. Mouth of the abdomen closed by a lattice-plate. | | Cephalis without porous tubes, | 494. Botryocampe. |
| Cephalis with a variable number of porous tubes, | 495. Phormobotrys. |
I. Subfamily Botryocyrtida. Mouth of the abdomen open. | ||||
| Cephalis without porous tubes, | ||||
| 492. Botryocyrtis. | ||||
| Cephalis with a variable number of porous tubes, | ||||
| 493. Pylobotrys. | ||||
II. Subfamily Botryocampida. Mouth of the abdomen closed by a lattice-plate. | ||||
| Cephalis without porous tubes, | ||||
| 494. Botryocampe. | ||||
| Cephalis with a variable number of porous tubes, | ||||
| 495. Phormobotrys. | ||||