ALCYONIUM. 



G9 



together upon one stem ; and one specimen is 

 described, in which two stems arise from the same 

 base, the one terminating with three, the other with 

 five lobes. A more particular account of these very 

 curious and interesting fossils may be found in the 

 Geological Transactions, and also in the description 

 of them by Miss Bennet. Under the second genus 

 we find the fossil before alluded to as described by 

 M. Mantell, and the name Mantellia is given it as a 

 compliment to that gentleman. 



Of the third genus many highly interesting spe- 

 cimens are also to be met with, generally imbedded 

 in flint or chalk ; and, indeed, they may be said to 

 be almost entirely confined to the chalk formation, 

 but slight traces of them being to be met with 

 elsewhere. 



Since the publication of the works now referred to 

 but little has been done as to the general arrange- 

 ment of these fossils. The fig-shaped ones described 

 by M. Guettard have been formed into a new genus 

 under the name of choanites ; and the genus ventri- 

 culites has been established for the reception of the 

 fossil discovered by Mr. Mantell, and described under 

 this name by him in his late very valuable and highly 

 comprehensive work, " The Geology of the South- 

 East of England ;" and as the whole description is 

 full of interest, and gives proof of the very great 

 research for which this gentleman is so justly cele- 

 brated, we shall, for the information of our readers, 

 give a condensed abstract of it. He describes the 

 ventriculite as a zoophyte of a funnel-shape, having 

 the base provided with radical fibres, or processes of 

 attachment, the external surface reticulated, the inner 

 covered with minute perforated papillae. The ori- 

 ginal substance was spongeous or gelatinous, and the 

 zoophyte was probably capable of expansion and 

 contraction. The common species, the radiatus, has 

 the external integument formed of subcylindrical 

 anastomosing fibres radiating from the centre to the 

 circumference ; the papillae on the inner surface are 

 formed by the open extremities of short transverse 

 tiilmli. This fossil assumes a great variety of forms, 

 and consequently it is necessary to examine a con- 

 siderable number of specimens in order to form pro- 

 per conclusions respecting it. Those which are 

 enveloped in flint are usually cup-shaped or tur- 

 1 /mated, while those imbedded in chalk exhibit a 

 broad circular disk ; the external surface presents a 

 number of cylindrical fibres extending in a radiating 

 manner from' the centre or base to the outer margin, 

 and by their frequent divisions and anastomising con- 

 stitute a reticulated integument capable of considerable 

 contraction and expansion. In its contracted cylin- 

 drical form it is from one to six inches in length ; 

 when expanded its diameter occasionally exceeds 

 nine inches ; the thickness of its substance is seldom 

 more than 0"2 of an inch. 



A specimen, figured in the work from which this 

 abstract has been taken, exhibits a narrow zone of 

 flint surrounding the wider part of the fossil (which 

 is funnel-shaped) at a small distance from the outer 

 edn-e ; when, from any cause, the included zoophyte 

 is destroyed, the ring remaining uninjured, presents 

 the appearance of a broad flat ring, and thus affords 

 a satisfactory solution of the origin of those broad 

 annular flints resembling a quoit, which are occa- 

 sionally found on the ploughed land of the downs of 

 Sussex. It also leads to the singular conclusion that 

 the silex, at the period of its mineralisation, was in the 



state of a thick viscid fluid, otherwise it is difficult to 

 understand why it should not extend to the margin, 

 instead of being consolidated in a ring at a short 

 distance from it. 



The inferences drawn from a careful examination 

 of these fossils lead also to a very satisfactory ex- 

 planation of the structure of the ventriculite when 

 living. 



Its general form appears to have been that of a 

 hollow inverted cone, having numerous branching 

 fibres proceeding from the base attaching it to other 

 bodies. Externally it was composed of a reticulated 

 integument capable of expanding or contracting ac 

 cording to the impressions received, and internally it 

 possessed a surface covered with the apertures of 

 numerous tubuli, probably the openings of vessels by 

 which nutrition was effected. Its expanded state 

 was possibly favourable for the discovery of the sub- 

 stances destined for its nutriment, which, by the 

 subsequent contraction would be imprisoned in the 

 funnel-like cavity, the nutritious particles being pro- 

 bably absorbed by the openings so numerously 

 distributed on its surface. Whether they were 

 capable of changing their situation by detaching 

 their radical processes cannot now be ascertained ; 

 but it is probably that, like the actinias and alcy- 

 onia, they were permanently fixed to the rock on 

 which they grew. 



The alcyonite fossils are found in various situa- 

 tions. Those of the tubular fruit-like forms are 

 found chiefly in the green sand. The ventriculites 

 and other bodies referable to this class are prin- 

 cipally met with either imbedded in chalk or in the 

 flint which is so abundant in their formation- The 

 diluvial gravel is also full of them. Those remark- 

 able masses of flint found in great abundance in 

 Ireland, and also in other places, called paramandra, 

 have every appearance of having been formed round 

 some species of tubercular alcyonia, which must have 

 been of enormous magnitude. We may also state, 

 that those singular hollow nodules, known in the 

 days of superstition and ignorance by the name of 

 eagle stones, and to which many magical as well as 

 medicinal properties, such as the preventing abortion 

 and the discovery of thieves, were attributed, have 

 also been referred to this class. They consist of 

 a flinty covering, probably formed over a sponge 

 or alcyonium, which decaying, has left a cavity in 

 the interior, the chalky, earthy, or silicious remains 

 of which occasion the rattling heard upon shaking 

 them. They were called eagle stones from the 

 ridiculous opinion that they were carried by the eagle 

 into her nest, in order to prevent the eggs from 

 becoming addled. They are now called geodes. 



After all that has been said, our readers must be 

 aware of the great difficulty experienced by men of 

 science in accurately classing or describing animals 

 of so changeable a nature. As zoophytes in general 

 are constantly in motion in quest of food, and yield 

 without difficulty in every direction to the slightest 

 pressure, the animals, when imbedded, might have 

 been softly covered or rudely crushed, and thus we 

 may account for the immense variety of forms under 

 which they have been discovered. 



ALCYONIUM, forms the fourth class of poly- 

 pidoms not subdivided into orders. It includes all 

 such as are called carnoid or flesh-like polypidopis, 

 being composed of a fleshy mass, wholly animated, 

 entirely covered with polypi, and possessing no ecu- 



