Page:Scientific results HMS Challenger vol 18 part 2.djvu/403

Rh 3. Anthocyrtidium matricaria, n. sp.

Shell campanulate, rough, very similar to the preceding species, but differing in the straight, large, pyramidal horn of the cephalis (as long as the shell), and in the longer feet, which are twelve to fifteen in number, little curved at the distal end, pointed, and about as long as the shell. Length of the two joints = 2 : 6, breadth = 3 : 8. Differs from the similar Anthocyrtium centaurea, Ehrenberg (1875, loc. cit., Taf. vi. fig. 5), mainly in the prominent ring of the peristome.

Dimensions.—Cephalis 0.02 long, 0.03 broad; thorax 0.06 long, 0.08 broad.

Habitat.—Fossil in Barbados.

Definition.— (vel Dicyrtida multiradiata aperta) without thoracic ribs, with numerous terminal feet around the mouth (six to twelve or more). Cephalis hidden in the thorax, without apical horn.

The genus Carpocanium, very common, and rich in numerous living and fossil species, was formerly placed by me among the true Monocyrtida, since an external constriction is not visible (Monogr., 1862, p. 290). Afterwards (in 1879) Richard Hertwig demonstrated that the cavity of the ovate shell, externally simple, is divided by an internal transverse septum into two joints, the upper of which is the flat rudimentary cephalis (Organism. d. Radiol., p. 79; compare also Bütschli, 1882, loc. cit., p. 535). Indeed this septum, with four central crossed cortinar beams, is a true collar septum, and Carpocanium has been derived from Anthocyrtis or Desmospyris by reduction of the cephalis, which is very flat and perfectly hidden in the uppermost part of the thorax. The apical horn is lost. If the internal septum were to become lost, the genus would pass over into Carpocanistrum.

Definition.—Peristome-corona composed of six feet (three primary perradial alternating with three secondary interradial).

1. Carpocanium calycodes, Stöhr.

Carpocanium calycodes, Stöhr, 1880, Palæontogr., vol. xxvi. p. 96, Taf. iii. fig. 8.

Shell urceolate, smooth, nearly twice as long as broad, with hemispherical vaulted cephalis. Length of the two joints = 3 : 16, breadth = 5 : 10. Pores regular, circular, as broad as the bars,