of the Ventriculidse of the Chalk. 293 



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 and 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. PI. 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 

 does not divide into lobes, as in Brachiolites : there is simply, in 

 order to ensure the greater security of the whole polypiferous 

 surface, an occasional constriction of the head and narrowing of 

 the plaits attached to it ; which plaits expand again, like an open 

 fan, in the following compartment. 



The appearance of the plaits themselves is very remarkable. 

 Their frequent constrictions give them a puckered or zigzag ap- 

 pearance, so that a vertical section pj^ ^ 

 has a figure of this kind. This 

 figure shows, also, how the pro- 

 jecting points of the plaits are 

 often attached, for security, to 

 the head. When the body is broken away the cast left is very 

 curious, the matrix being always broken ofi" in many of the places 

 where it has filled a pucker in the upper plait, depressed where 

 there was a pucker in the lower plait. This is seen on the right 

 hand of fig. l.Pl. XV. 



