Arms nearly lanceolate, twice as long as broad, half as broad at the base as at the broadest middle part, pointed at the distal end. Patagium complete, enveloping the whole triangular disk, with irregular chamber-rows.
Dimensions.—Radius of the arms 0.2, breadth on their base 0.04, on the broadest part 0.08.
Habitat.—Mediterranean (Messina), surface.
3. Hymeniastrum gümbelii, Haeckel.
Stylactis gümbelii, Stöhr, 1880, Palæontogr., vol. xxvi. p. 112, Taf. vi. fig. 1.
Arms twice as long as broad, nearly twice as broad in the circular distal half as in the square proximal half. Patagium incomplete, circular, with eight to nine convex chamber-rows, enveloping only the proximal square halves of the arms; the lenticular distal halves remain free.
Dimensions.—Radius of the arms 0.14; breadth at the base 0.04, at the distal lenticular part 0.07.
Habitat.—Fossil in the Tertiary rocks of Sicily, Grotte, Stöhr.
4. Hymeniastrum euclidis, n. sp. (Pl. [43], fig. 13).
Euchitonia euclidis, Haeckel, 1881, Prodromus, p. 460 et Atlas (pl. xliii. fig. 13).