_Sycidium melo._ (Sandb.) Fig. 32, _B._ The specimen represented in fig. 32, B (i), (ii), drawn from Deecke’s figures[322], has the form of a small oval calcareous body, 1 mm. in transverse diameter and 1–1·3 mm. in longitudinal diameter. It is pointed at one end and flattened at the other. At the flatter end there is a circular depression, continued into a funnel-shaped cavity, and on the walls of this cavity there are 18–20 radially disposed ribs, which extend over the surface of the whole body. A series of transverse ribs intersects the vertical ribs at right angles. The calcareous wall is perforated by numerous whorls of circular pores, and the internal cavity is a simple undivided space. Each of these oval bodies (fig. 33, B) is probably the segment of a thallus, and the perforations in the wall may have been originally occupied by lateral prolongations from the unseptate axial cell of the thallus. _Sycidium_ bears a fairly close resemblance to the Tertiary _Ovulites_. _Diplopora._ Fig. 35, A and B. This genus of algae is characteristic of Triassic rocks, and is especially abundant in Muschelkalk and Lower Keuper limestones of the Alps, Silesia, and elsewhere. The thallus, or rather the calcareous portion of the thallus, has the form of a thick-walled tube, with a diameter of about 4 mm., and occasionally reaching a length of 50 mm. At one end the tube has a rounded and closed termination, and the wall is pierced throughout its whole length by regular whorls of fine canals. _Diplopora_ agrees with _Cymopolia_ in its main features. [Illustration: FIG. 35. A, B, _Diplopora._ × 2. C, D, _Gyroporella_ (after Benecke. × 4). E, Calcareous segments of _Penicillus_, from a specimen in the British Museum. × 5. F, a single segment of _Ovulites margaritula_ Lam. × 4. G, _Confervites chantransioides_ Born. (after Bornemann. × 150).]