ADDENDA. 
(See Plate CXVIa.) 
The following description and illustrations of Cohnulites are from Murchi¬ 
son’s “ Silurian System,” published in 1839. 
Under the head of “Fossil Shells of the Wenlock Limestone,” J. De C. 
Sowerby describes Cornulites serpulai'ius, as follows; 
“ Cornulites serpularius, Schlot., pi. xxvi, f. 5 (Schloth. Petr., t. xxix, f. 7). 
We can scarcely attempt a description of this anomalous fossil, of which at 
present but one species is known. So unlike is it to anything we have seen, 
that we are unable to assign it a place in the system of animals, or draw a 
comparison between it and any oth6r creature. Its general form is a much 
elongated, hollow, more or less crooked cone, open at the base; in its early 
state it is parasitical, being attached by its side and often in pairs. The exter- 
•nal crust is longitudinally striated, and marked with slightly raised rings, which 
indicate its passage over the margins of the series of truncated cones of which 
the fabric is constructed. These short cones are placed within each other, their 
widest edges being directed toward the apex of the general envelope, the small¬ 
est or most internal cone occupying the apex itself Thus they form a pyramid 
of cups, or if viewed in a reverse position, a series of broad rings gradually 
increasing in size, and capping but not covering each other. Each cup or ring 
is thinnest at that part which is inclosed by the succeeding ring, where also its 
diameter is least; both surfaces are of a foliated structure, and the outer blends 
with and is lost in the external coat. Internally, each ring was apparently of 
a cellular structure, for it is composed of depressed, imbricating, and regularly 
arranged grains of calcareous spar. Some of the grains leave an impression 
upon the surface of each of the steps, which is formed upon the cast of the 
cavity of the cone by the thick edges of the rings. 
“ If the cells were the habitations of minute Polypes, they must have opened 
upon the edge of the cup, and each succeeding generation must have been 
located around the parent stock, and not upon or within the Polyparium, as in 
corals; but there is no appearance of steiloe or radiating laminae. Upon the 
cast of the inner cavity may often be observed two, three, or more longitudinal 
impressions, each composed of two nearly approximating, fine, sunken lines, 
produced by elevations where probably there were joinings in the cups. The 
