Shell hemispherical, spiny, with irregular polygonal pores. Basal plate with six meshes (?). Between the smaller spines of the surface arise six larger conical divergent horns. Three feet also conical, divergent, about twice as long as the shell and the horns. _Dimensions._--Shell 0.05 long, 0.07 broad; horns 0.05 long, feet 0.1 long. _Habitat._--Central Pacific, Station 274, depth 2750 fathoms. {1157}Genus 510. _Archibursa_,[127] Haeckel, 1881, Prodromus, p. 429. _Definition._--#Archiperida# (vel Monocyrtida triradiata clausa) without internal columella and without apical horn. The genus _Archibursa_ has probably arisen from _Peridium_ by loss of the apical horn, and is the only genus of Archiperida which bears no horn. The three basal feet are well-developed. It differs from the similar _Tristylospyris_ by the absence of the sagittal ring and the corresponding longitudinal constriction. 1. _Archibursa tripodiscus_, n. sp. (Pl. 98, fig. 6). Shell subspherical, smooth, with irregular roundish pores. Basal plate with three large triangular pores of equal size (fig. 6). Three feet widely divergent, straight, three-sided prismatic, about as long as the diameter of the shell. _Dimensions._--Diameter of the shell 0.07, length of the feet 0.09. _Habitat._--Central Pacific, Station 272, depth 2600 fathoms. Family LX. #PHÆNOCALPIDA#, n. fam. _Archiphormida_ et _Archiphænida_, Haeckel, 1881, Prodromus, pp. 428, 429. _Definition._--#Monocyrtida# multiradiata. (#Cyrtoidea# with a simple, not jointed shell, resembling a simple cephalis, with numerous radial apophyses (four to nine or more). The family #Phænocalpida#, composed of the Archiphormida and Archiphænida of my Prodromus, comprises those #Cyrtoidea# in which the lattice-shell is quite without transverse constriction, but bears numerous radial apophyses. The two subfamilies differ in the shape of the basal mouth, which in the Archiphormida is a simple wide opening, but is closed in the Archiphænida by a lattice-plate. Several Phænocalpida were formerly described by Ehrenberg, viz., _Halicalyptra virginica_ (in 1844) and _Litharachnium arachnodiscus_ (in 1872, called by him _Carpocanium_, though it is quite different from this genus, and closely allied to my _Litharachnium tentorium_, figured in 1862). These forms belong to the Archiphormida (with open mouth). Several fossil Archiphænida (with closed mouth) were figured by Ehrenberg, in 1875, as belonging to _Petalospyris_ (_ocellata_, _carinata_, _flabellum_), though the absence of the sagittal ring and the corresponding longitudinal constriction demonstrates their character as _Phænocalpis_.