_Definition._--#Lithobotryida# with tubes on the cephalis, and with the mouth of the thorax open. The genus _Acrobotrys_ differs from the preceding _Botryopyle_ in the development of radial tubes, and from its probable ancestral form, _Cannobotrys_, in the development of a thorax, the basal mouth of which remains open. According to the varying number of the tubes we may distinguish the following five subgenera (corresponding to those of _Cannobotrys_), viz., (1) _Acrobotrantha_ (_monosolenia_) with a single (apical) tube; (2) _Acrobotrella_ (_disolenia_) with two divergent tubes (an apical and a sternal); (3) _Acrobotrissa_ (_trisolenia_) with three sagittal tubes (an apical, a caudal, and a sternal); (4) _Acrobotromma_ (_tetrasolenia_) with four tubes, like the four typical spines of _Cortina_; and (5) _Acrobotrusa_ (_pentasolenia_) with five feet, corresponding to the five typical spines of _Stephanium_. 1. _Acrobotrys monosolenia_, n. sp. Cephalis trilobate, with a single straight apical tube, which ascends vertically from the apex of the occipital lobe, and is pointed at the distal end, with an anterior oblique aperture. Two frontal lobes paired, ovate, half as long as the helmet-shaped occipital lobe. Thorax ovate, twice as long as the cephalis. Pores very scarce. _Dimensions._--Length of the shell 0.08, breadth 0.06. _Habitat._--Mediterranean (Corfu), surface. 2. _Acrobotrys disolenia_, n. sp. (Pl. 96, fig. 10). Cephalis trilobate, with three odd ovate lobes of nearly equal size in the sagittal plane and two divergent straight slender cylindrical tubes, a vertical apical tube on the occipital lobe, and a horizontal nasal tube on the frontal lobe; the middle lobe between them is somewhat smaller. Thorax ovate, about twice as large as the cephalis, with constricted mouth. Pores small and numerous. _Dimensions._--Length of the shell 0.1, breadth 0.06. _Habitat._--Central Pacific, Station 265 to 274, depth 2350 to 2925 fathoms. 3. _Acrobotrys aquaria_, n. sp. Cephalis quinquelobate, with two divergent long cylindrical curved tubes. Occipital lobe helmet-shaped, with an ascending apical tube; nasal lobe conical, with a descending sternal tube; {1115}between them a smaller odd middle lobe, and on each side of the latter an ovate frontal lobe. Thorax inflate, twice as long and broad as the cephalis. Pores small, scarce. _Dimensions._--Length of the shell 0.09, breadth 0.07. _Habitat._--South Pacific, Station 285, depth 2375 fathoms. 4. _Acrobotrys acuminata_, n. sp. (Pl. 96, fig. 9). Cephalis sexlobate, with two divergent tubes. Occipital and frontal lobes ovate, odd; between them a cupola-shaped apical lobe, bearing an ascending pointed apical tube. On each side at the base a small buccal lobe, and between the paired buccal lobes an anterior nasal lobe with a descending curved sternal tube. Thorax smaller than the cephalis. Pores numerous and small. _Dimensions._--Length of the shell 0.11, breadth 0.09.