19 
Description. 
1 have derived the specific name RoTUNDUS, from the animal having a round 
column. 
The remains of the AprlocniniTEs ROTUNDUS have as yet only occurred in a 
fossil state, and no perfect specimen has been met with. At Bradford the al- 
most shapeless bases (Pu. u. fig. 1. and 9.) of this species are met with, adhering 
tothe surface of the oolitic rock, of various sizes, inclosing portions of the column, 
which are seen externally shooting forth from them. They are affixed in great 
number to each other, and not unfrequently to testacea and other extraneous 
marine bodies, which proves that the animal lived in the sea, and affixed itself 
wherever chance directed its ovum. Portions of the column (PL. tv. fig. 1.) the 
animal's superior pear-shaped part (PL. 1. fig. 2.) and the separate juints of 
both are generally found in the clay which covers the oolite. As cellepores 
shells and serpule (Pu. 1. fig. 9) adhere to them, they must have been of a 
firm texture, and as these frequently occupy the inner surfaces of joints (PL. 1. 
fig. 1) the remains of these animals must have lain for some time in a dead and 
separated state, before they were covered with the mass of the stratum in which 
they are imbedded. The comparatively rare occurrence of portions of the 
column, its short fragments, on which I never could trace the slightest mark 
indicating side arms, and the bulky superior part, point out that the column at 
no time could have been very long (PL. 1. fig. 1.) since otherwise the animal 
would have been continually in danger of mutilation from the over poising 
weight of its superior part; and the more so as from its want of side arms it 
could have possessed no lateral support to counteract this weight. — 
The Couumy, as has been observed, is formed of numerous round depressed 
joints (PL. rv. fig. ] and 6) pierced in the centre to afford a passage to the 
alimentary canal (PL. rv. fig. 20.—PL. 111. fig. 4.) Their upper and lower sur- 
faces are striated in radii, of which the depressed spaces adinit the elevated ones 
of the next joint. The radii are at certain distances interrupted by concentric 
of (more or less)elevated rings, parallel to the circumference of the column, which 
are more conspicuous towards its apex. (PL. Iv. fig. 8,9, and 14.) At each of 
these interruptions the radii divide (forming sometimes minute tubercles) thus 
increasing their number as the animal grows, This increase of the number of 
