Dimensions.—Length of the shell 0.1, breadth 0.05.
Habitat.—South Pacific Station 297, depth 1775 fathoms.
Genus 491. Lithobotrys,[[108]] Ehrenberg, 1844, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, p. 74.
Definition.—Lithobotryida with tubes on the cephalis, and with the mouth of the thorax closed.
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.
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.