Shell nearly ovate, strongly compressed, smooth, one and a half times as long as broad, with deep sagittal stricture in the basal half. Pores very small and numerous, irregularly roundish. Basal plate with four very large triangular holes, two larger (posterior) cardinal, and two smaller (anterior) {1046}jugular pores; above the latter (on the frontal face) two large mental pores. Two pectoral feet large, half as long as the shell, at the base fenestrated, vertical, and parallel. Two sagittal feet much smaller, nearly horizontal, pyramidal (the caudal larger than the sternal foot). Two longitudinal pectoral ribs arise on the frontal face. _Dimensions._--Shell 0.21 long, 0.14 broad; lateral feet 0.1, sagittal feet 0.02. _Habitat._--South Atlantic, Station 332, depth 2200 fathoms. 2. _Tessarospyris nuciformis_, n. sp. Shell nut-shaped, papillate, with deep sagittal stricture. Pores irregular roundish, on both sides of the ring three to six times as large as on the lateral sides. Basal plate with four large pores. Two pectoral feet cylindrical curved, twice as long as the shell and as the two sagittal feet; the caudal is much stronger than the sternal foot. _Dimensions._--Shell 0.06 long, 0.09 broad; lateral feet 0.1, sagittal feet 0.05 long. _Habitat._--Tropical Atlantic, Station 347, depth 2250 fathoms. 3. _Tessarospyris seminulum_, Haeckel. _Petalospyris seminulum_, Stöhr, 1880, Palæontogr., vol. xxvi. pl. iii. fig. 12. Shell subspherical, smooth, with slight sagittal stricture and small circular pores; some larger pores on both sides of the ring. Basal plate with two large (lateral) pores only. Four feet nearly equal, short, conical, divergent, scarcely one-fourth as long as the shell. _Dimensions._--Shell 0.06 long, 0.08 broad; feet 0.016 long. _Habitat._--Fossil in Tertiary rocks of Sicily (Grotte), Stöhr. Subfamily 4. HEXASPYRIDA, Haeckel. _Definition._--#Zygospyrida# hexapoda, with six descending basal feet; three of these are primary (one odd caudal and two paired pectoral feet), the other three are secondary, opposed diametrically to the former and alternating with them (one odd sternal and two paired tergal feet). Genus 453. _Hexaspyris_,[71] n. gen. _Definition._--#Zygospyrida# with six basal feet and one apical horn. The genus _Hexaspyris_ and the two following closely allied genera represent together the peculiar subfamily of Hexaspyrida, and differ from the other Zygospyrida in the possession of six descending basal feet; three of these are the three original, perradial, or primary basal feet of _Cortina_, _Cortiniscus_, _Plagoniscus_, _Plectaniscus_, _Tripospyris_, &c.; the other three, usually opposed to the former diametrically, are {1047}secondary or interradial; an odd sternal foot (opposed to the odd caudal) and two paired tergal feet (opposed to the two paired pectoral). Subgenus 1. _Hexaspyridium_, Haeckel. _Definition._--Feet simple, not branched nor forked. 1. _Hexaspyris alterna_, n. sp.