85 



at considerable intervals, with a single opening in the middle 

 of each compartment thus caused. 



The specific description will satisfy the inquirer that this is a 

 very extraordinary form. Externally it has nothing which would 

 indicate any Ventriculitic affinity, and it has indeed been described 

 by Dr. Mantell under the name of Choanites subrotundus ; but it 

 has no relation whatever to Choanites. The appearance of the 

 fossils is so remarkable, that, but for the fixed rule of preserving 

 every fragment which I could not understand, I should never 

 have been able to establish or even suspect the true affinities. 

 A suite of seventeen specimens enables me, however, now to point 

 out the true general characters of the species without leaving 

 any room even for doubt. 



In the two very different states in which the fossil, or frag- 

 ments of it, are found, it has very different appearances ; the one 

 state (see left hand of figure) shows the upper, the other (see 

 right hand of figure) the lower part only, or its cast. The com- 

 parison of several of these apparently anomalous fossils led me 

 however to conceive that the connected rounded bodies seen in 

 the former set of specimens had some relation to the very pe- 

 culiarly complicated and almost angularly raised surfaces seen in 

 the latter. With this clue I cut down some of these rounded 

 bodies, and found the identical surfaces last named below them. 

 Several sections being made, and the whole series being then 

 compared, order and method became at once apparent where all 

 had previously been anomaly and confusion. The characteristic 

 Ventriculitic structure was detected : the Ventriculitic fold was 

 traced : and the Ventriculitic root Was found. 



I conceive the habit of the animal to have been very different 

 in one respect from that of all the species which have hitherto 

 engaged attention. While the .latter stood rising upwards from 

 a central root, this species, attached at one end by a root, and thus 

 secured in its position, floated horizontally, like a ship riding at 

 anchor. It had therefore no central cavity in the direction of its 

 length, but, instead of this, it was covered by a head investing 

 the upper arid lateral surfaces of that whole length ; and which 

 head, with rare exceptions, for such exceptions do exist, was con- 

 stricted at intervals, causing the animal, when seen from above 

 and entire, as in the greater part of fig. 1. PL XV., to appear 

 like several distinct globose bodies linked together. The fact 

 of the head being occasionally, though rarely, not constricted at 

 all, will satisfy any philosophic inquirer that such an appearance 

 is deceptive, and that the explanation thus given of that appear- 

 ance is the true one. Besides this, however, if the head be re- 

 moved, and the lower surface of the fossil only seen, all trace of 

 separation and distinctness is gone. The membrane of the wall 



