1888-89.] Mr John Rattray on the Genus Coscinodiscus. 665 
T. Korman !) ; Atlantic soundings (Ralfs) ; Gazelle Expedition, 
Yokohama (Schmidt) ; Pabellan di Pico guano (Deby !) ; Holo- 
thuria , China (Deby!); Faeroe Islands, H.M.S. Knight Errant 
(Grove !) ; loc.? (Grove !). 
Aster om. arachne. Spatangidium arachne , de Br4b., Bull. Soc. 
Linn. Normand ., 18D7, p. 296, pi. iii. tig. 1. — Broadly ovate to 
subcircular. Diam. '045 to *06 mm. Markings : rays 5, the 
central subobsolete longest, its proximal end expanded, malleiform, 
reaching between proximal ends of lateral rays, excentric ; the 
lateral rays in two nnsymmetrical pairs, the lower pair substraight, 
or slightly convex towards the central ray, the upper pair more 
curved in their proximal portions and more convex towards the 
lower ; their inner ends expanded hut more rounded than that of 
central ray ; their outer ends sometimes slightly swollen and not 
reaching the border; compartments of unequal length, their inner 
ends convex, that opposite the subobsolete ray concave inwards, 
the areolae, decreasing but slightly outwards, 6 to 7 in *01 mm.; 
rows evident, those adjacent to the rays somewhat more prominent. 
Border narrow, hyaline. — Ralfs in Priteh. Inf., p. 837; Sch., Atl., 
pi. xxxviii. figs. 3, 4 ; Aster om. malleus, Wallich, Trans. Micr. Soc. 
Bond., 1860, p. 47, pi. ii. fig. 11 ; Asterom. malleiformis, Wallich, 
ibid., Explan. pi. ii. fig. 11; Asterolampra arachne, Grev., Trans. 
Micr. Soc. Lond., 1860, p. 123; Excentron cancroides , Ralfs, ibid., 
p. 837. 
Habitat. — Peruvian guano (Greville ! Grove !) ; Ichahoe guano 
(Korman !) ; Indian Ocean soundings, 2200 fathoms, by Capt. 
Pullen (Greville !) ; locality ? (Dickie !) ; from Salpoe, Indian 
Ocean (Wallich) ; Guanape guano (Deby !) ; Arica, and Gazelle 
Expedition (Schmidt) ; S.S. Buccaneer, off Ascension Island 
(Grove !). 
Asterom. nanicoorensis. Grun., Reise d. Novara, 1870, p. 104, 
pi. i. a. fig. 22. — Oval to subcircular. Length, *065 to ’075 mm.; 
breadth, -0625 to * 065 mm. Centro-lateral area with sides concave 
outwards, the inner end conical. Markings excentrically disposed ; 
rays — one more robust, arcuate, proceeding from apex of centro- 
lateral area, a few others more delicate ; the compartments of 
unequal lengths, their inner ends concave towards centre ; areolae 
