1852.] LYELL BELGIAN TERTIARY FORMATIONS. 347 



the peduncle appears to Dr. Hooker to be unlike plant-structure. 

 Some Sponges, on the other hand, offer a similar appearance. 



PL XX. fig. 1 . represents this fossil, of the natural size. It is a 

 cast of a transversely obtuse-oval body, with a sinus on its upper or 

 longer edge, and opposite to this a stem-like tapering projection or 

 peduncle. This surface of the cast is convex, and the other surface, 

 on the corresponding fragment of the nodule, which has not been 

 preserved, was probably parallel to it, a slight cavity intervening; 

 traces of a furrow at the margin of the cast (fig. 5 a) remain to indi- 

 cate the thickness of the blunt edges of the Honium, which was pro- 

 bably less than y^Qth of an inch. The stem or peduncle was continued 

 into the body, as shown by a granular ridge upon the surface of the 

 cast ; in other words, a thin ridge runs from about the centre of the 

 surface of the body down towards the peduncle. Imbedded in the 

 surface of this specimen are seen clusters of spicula ; and a small 

 portion of it retains a reticulated surface, which is still better shown 

 in the specimen fig. 2, where at one spot the reticulation passes over 

 the spines. 



PI. XX. fig. 6° and 6*. — Magnified representations of the spicula 

 from the above-described specimen, fig. 1 ; «, and c, c, Spicula of 

 Sponge ?, b and d, Spines of a Spatangus, 



All of these are more or less coated with the same earthy matter 

 which cements the sandstone in which they are imbedded. The 

 grains of sand being enveloped with the same calcareo-siliceous cement, 

 are thus often joined to the spicula, and when these grains happen to 

 adhere to the end of a spiculum they give it the appearance of a spine 

 with a bulbous base. The spicula vary in length from -jV ^^ i^ inch. 



Fig, 2. (Natural size.) — Another specimen of Honium. Only a 

 few spicula are dispersed over it, and the surface is nearly covered by 

 a fine network. 



Fig. 3. — A portion from near the centre of the surface of fig. 2, 

 magnified. 



Fig. 4. — Another portion from the central part of the same speci- 

 men, showing the reticulated surface, 6, converging towards, and 

 passing under the granular ridge, a. 



Fig. 5, a. — Magnified representation of part of the surface at the 

 edge near the stem, on the right-hand side of fig. 2. 



Fig. 5, b. — Portion of the surface in the sinus (fig. 2), where the 

 network assumes the aspect of a wrinkled membrane, or of a mem- 

 brane to which a cellular tissue has been attached, the rest of the 

 tissue being destroyed. 



Patches of a black, carbonaceous, pulverulent matter stain the 

 hollows in both specimens. 



It appears that the stony beds at Schaerbeek (III. «, Table XII. 

 p. 334), which contain the above-mentioned Honium and Nipadites, 

 with much fossil wood of palms and dicotyledonous trees, were formed 

 in the sea, near the mouth of a river, as in the case of the clay at 

 Sheppey ; and the fruits prove that the same species of Nipadites 

 which flourished at the period of the London Clay proper continued 



