Habitat.—South Pacific, Station 295, depth 1500 fathoms.
3. Larnacidium polybelonium, n. sp.
Cortical shell very spiny, with numerous (twenty to thirty or more) larger thin radial spines, about as long as the shell. Pores irregular, twice to five times as broad as the bars; about sixteen on the half meridian. Proportion of the three axes = 2 : 2.5 : 3. Medullary shell lentelliptical, half as large as the cortical shell.
Dimensions.—Length of the cortical shell 0.11, breadth 0.09, height 0.07; pores 0.004 to 0.01, bars 0.002; length of the medullary shell 0.06, breadth 0.05, height 0.04.
Habitat.—Western Tropical Pacific, Station 225. depth 4475 fathoms.
Subfamily 2. Larnacalpida, Haeckel.
Definition.—Larnacida with a double, trizonal, Larnacilla-shaped medullary shell, enclosed in the central capsule, and enveloped by a simple or double, latticed or spongy, lentelliptical, cortical shell.
Genus 274. Larnacalpis,[[313]] n. gen.
Definition.—Larnacida with a simple lentelliptical cortical shell, without radial spines. Medullary shell double, Larnacilla-shaped.
The genus Larnacalpis represents the most simple form of the sub-family Larnacalpida, and is very important as the common original form of all those Larcoidea in which a double Larnacilla-shaped medullary shell is surrounded by a simple, perfectly closed, latticed, lentelliptical cortical shell. Therefore the same typical, trizonal, lentelliptical shell, which in Larnacilla represents the external envelop (or cortical shell) of the central capsule, here in Larnacalpis becomes enclosed as an internal nucleus (or medullary shell) in the interior of the central capsule, and this latter becomes overgrown by a new lentelliptical cortical shell. The connection between the two shells of Larnacalpis is either effected by a number of radial beams (e.g., in Larnacalpis triaxonia by six beams situated in the three dimensive axes), or by two lateral, latticed, tube-like wings, which are repetitions of the smaller lateral wings connecting its external shell with the internal medullary shell (as in Larnacalpis lentellipsis). The latter species may be regarded as a Pylonium with a completely latticed shell.