Sagittal ring ovate, thorny, with three prominent, distorted edges; its dorsal rod nearly straight and vertical, with one or two pairs of short thorns; its ventral rod strongly curved, with three or four pairs of divergent thorns. Basal ring larger than the sagittal ring, with two semicircular gates and obliquely ascending halves, which on the inner and lower edge are smooth, {964}on the outer and upper thorny. Apical horn and the three divergent feet nearly equal, straight, about as long as the sagittal ring, with three thorny edges. _Dimensions._--Height of the sagittal ring 0.1 to 0.12, breadth 0.07 to 0.09. _Habitat._--Central Pacific, Stations 270 to 274, depth 2350 to 2925 fathoms. 2. _Cortiniscus dipylaris_, n. sp. (Pl. 92, fig. 13). Sagittal ring nearly semicircular, with prominent distorted edges and six pairs of small roundish papillate tubercles (three pairs on the straight dorsal, three on the curved ventral rod). Apical horn short and stout, with a tuberculate knob. Basal ring smaller than the sagittal ring with two elliptical gates. Three feet short and stout, irregularly branched like a cauliflower, with numerous short papillate tubercles. _Dimensions._--Height of the sagittal ring 0.11, breadth 0.08. _Habitat._--Central Pacific, Station 268, depth 2900 fathoms. 3. _Cortiniscus tripylaris_, n. sp. Sagittal ring elliptical, smooth. Apical horn conical, smooth. Basal ring larger than the sagittal ring, with three elliptical gates of equal size; two paired, posterior (jugular pores) between the basal parts of the caudal foot and the two pectoral feet, and an odd, anterior (sternal pore) between the basal parts of the two pectoral feet and a connecting horizontal convex sternal bow. _Dimensions._--Height of the sagittal ring 0.09, breadth 0.06. _Habitat._--Tropical Atlantic, Station 348, depth 2450 fathoms. 4. _Cortiniscus tetrapylaris_, n. sp. Sagittal ring elliptical, with four pairs of short branched thorns, two posterior on the straight dorsal, and two anterior on the curved ventral rod. Basal ring smaller than the sagittal ring, with four triangular gates; the two anterior (jugular pores) a little smaller than the two posterior (cardinal pores). Apical horn and the three divergent feet shorter than the sagittal ring, irregularly branched, with curved, often tuberculate branches. _Dimensions._--Height of the sagittal ring 0.08 to 0.12, breadth 0.06 to 0.1. _Habitat._--Fossil in Barbados. 5. _Cortiniscus typicus_, n. sp. (Pl. 92, fig. 12).