Page:Scientific results HMS Challenger vol 18 part 1.djvu/799

Rh former. Arms club-shaped, their basal semi-cylindrical, half as broad as the spherical distal half, which bears a strong, conical, terminal spine. The discoverer of this remarkable, very old, Liassic species, Dunikowski, supposes that it is not a true Discoid, from the absence of a central disk; in my opinion the central disk (nearly spherical) has the same relation to the arms as in many other, their equatorial plane is the same.

Dimensions.—Radius of the odd arm 0.18, of the paired arms 0.24; basal breadth 0.08, distal breadth 0.16.

Habitat.—Fossil in the Alpine Lias, Schafberg, near Salzburg, Dunikowski.

6. Rhopalodictyum elongatum, n. sp.

Arms of different size and at unequal distances, one odd arm being twice as long as both paired arms; the odd angle between the latter much larger than both equal paired angles. Arms nearly cylindrical, little flattened, three to six times as long as broad, with rounded blunt distal end.

Dimensions.—Radius of the arms 0.15 to 0.3, breadth 0.05.

Habitat.—Pacific, central area, Station 274, surface.

7. Rhopalodictyum curvatum, n. sp.

Arms of different size and at unequal distances, irregular, more or less curved, nearly cylindrical, five to ten times as long as broad, with rounded blunt distal end. (There were observed only two specimens of this remarkable irregular species; in one specimen all three arms were simple, in the other one odd arm forked. The length of the arms and the size of the angles between them seems to be very different and variable.)

Dimensions.—Radius of the arms 0.3 to 0.6 to 1.15, breadth 0.06 to 0.12.

Habitat.—Pacific, central area, Station 271, surface.

Definition.— with three spongy arms on the margin of the circular or triangular disk, connected by a spongy patagium of different texture.

The genus Dictyocoryne differs from the foregoing Rhopalodictyum only in the patagium, connecting the three spongy arms, and bears to it the same relation as in the Porodiscida Euchitonia does to Rhopalastrum. The typical species of this genus is Dictyocoryne profunda, the only species figured by Ehrenberg. After his