The genus _Lithobotrys_, the oldest and first known of the #Botryodea#, was founded by Ehrenberg in 1844, and was one of his five oldest genera of Polycystina. It represented by itself the suborder #Botryodea# until the year 1860. The numerous species described by Ehrenberg belong to very different genera of #Botryodea#, and partly also of #Spyroidea#. Following Bütschli (1882) we retain here the name _Lithobotrys_ for those species, the type of which is _Lithobotrys geminata_. The genus _Lithocorythium_ of Ehrenberg is for the greater part identical with it. When in the preceding genus _Acrobotrys_ the mouth of the thorax becomes closed by lattice work, _Lithobotrys_ arises. In the latter as well as in the former the number of tubes on the cephalis is different, and may characterise different subgenera. {1118}1. _Lithobotrys geminata_, Ehrenberg. _Lithobotrys geminata_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 76, Taf. iii. fig. 19. _Lithobotrys geminata_, Bütschli, 1882, Zeitschr. f. wiss. Zool., vol. xxxvi, p. 519, Taf. xxxiii. fig. 27, a to c. ? _Lithocorythium platylophus_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iv. fig. 5. Cephalis trilobate, with a single apical tube in the apex of the helmet-shaped occipital lobe, which is one and a half times as long as the two subspherical frontal lobes. Thorax ovate, one and a half times as long as the cephalis, with few small pores in six to eight transverse rows. _Dimensions._--Length of the shell 0.1, breadth 0.05. _Habitat._--Fossil in Barbados. 2. _Lithobotrys lithocorythium_, Haeckel. _Lithocorythium oxylophus_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iv. figs. 3, 4. ? _Lithopera oxystauros_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 78, Taf. iii. fig. 6. Cephalis trilobate, with a single apical horn or a pointed tube in the apex of the helmet-shaped occipital lobe, which is a little longer than the two ovate frontal lobes. Thorax ovate, about as long as the cephalis, with very numerous and small pores. _Dimensions._--Length of the shell 0.08, breadth 0.04. _Habitat._--Fossil in Barbados. 3. _Lithobotrys nasuta_, Ehrenberg. _Lithobotrys nasuta_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 76, Taf. iii. fig. 21. Cephalis quadrilobate, with a single descending sternal or nasal tube on the base of the anterior or frontal lobe, which is half as long as the helmet-shaped occipital lobe and twice as large as the two lateral buccal lobes. Thorax ovate, twice as long as the cephalis. Pores rather large, circular. _Dimensions._--Length of the shell 0.11, broad 0.05. _Habitat._--Fossil in Barbados. 4. _Lithobotrys ornata_, Ehrenberg. _Lithobotrys ornata_, Ehrenberg, 1875, Abhandl. d. k. Akad. d. Wiss. Berlin, p. 76, Taf. iii. fig. 18.