VII.] SYCIDIUM. 173 



North German drifts The tubes have a diameter of '5 — 1 mm., 

 and are perforated by radial canals which probably mark the 

 position of verticils of branches given off at right angles to the 

 central axis. The surface of the tubes is divided into regular 

 hexagonal areas. 



The resemblance of these Silurian fossils to Diplopora 

 and other genera favours their inclusion in the Verticillate 

 Siphoneae. 



Sycidium, Fig. 32, B. 



The fossils included in this genus were first described by 

 Sandberger from the middle Devonian rocks of the Eifel, and 

 referred by him to the animal kingdom. More recently Deecke 

 has suggested the removal of the genus to the calcareous 

 Siphoneae, and such a view appears perfectly reasonable, 

 although without more data it is not possible to speak with 

 absolute certainty. 



Sycidium melo. (Sandb.) Fig. 32, B. The specimen repre- 

 sented in fig. 32, B (i), (ii), drawn from Deecke's figures^ 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. 



1 Stolley (93). ' Deecke (83). 



