DEXTALIUM. 



DKNTALIUM. 



and other genera analogous in appearance. In the ' Philosophic 

 Zoologique he separated the clan of worm* of the 'Syttemn' into two 



other nliiim, and formed the Annelide*, with the section of External 

 Worm* (Ver* Exteneun). He elevated, observes M. Deehaye*, thin 

 division sufficiently in the aerie* of /nrrrfrAm/u, the presence of a 

 heart and a circulation making it approximate to the Mollusks; whilst 

 the Worms, very inferior in organisation, remained between the soft 

 Radinm and the Insects. In this new class, add* M. Deahayes, we 

 find the ZAm/o/ia in the same section with Srrpula, fyirorif't, and 

 Siliqitario. This arrangement was not altered in ' L'Kxtrait dti 

 Coon,' published in l^ill. But, in the great work of the ' Auinmiix 

 sans Vertebra*,' Lamarck, assisted by the labours of Savigny, and 

 deceived moreover by the communications of M. Fleuriau de 

 Bellevue, considered ItentaJtum a* approximated to Clymenr, and 

 placed it in the family of Maldauians of H. Savigny. Systematic 

 author* generally, not knowing more than Lamarck did, that know- 

 ledge being confined to the tube, followed Lamarck's opinion. Cuvier, 

 in the first edition, placed it among the Anncluies Tubicoles, between 

 Atprryillnm (Patieillut, Lam.) and Siliguaria. Savigny, in his 

 'Systeme del Annuities,' gave a summary description of the animal, 

 but it was too incomplete to decide the question finally, though suffi- 

 cient to overthrow the observations of M. Fleuriau de Bellevue. The 

 D. Entalii, which was sent to Savigny by our countryman Leach, 

 gave sufficient information to that celebrated zoologist to enable 

 him to say that the animal had no trace of rings, that it hail no 

 hairs (soies) on the lateral parts of the body, that it was essentially 

 muscular, and that it could no longer remain among the Cluelojunln. 



D. Eittali* was the species on which H. Deshayes mode his obser- 

 vations ; and in a very interesting and elaborate paper read before tin- 

 Society of Natural History of Paris, on the 18th of March, 1825, he- 

 gave the fact* which led him to the conclusion stated at tin- 

 commencement of this article. The following is a summary of his 

 description : but we must premise that M. Deshayes'a specimens 

 were forwarded to him in spirit, and were consequently a good deal 

 contracted : 



Externally the animal is conical and elongated, like the shelly 

 investing tube (dorsal surface corresponding with the convexity of 

 the shell ; ventral surface corresponding with the concavity) ; smooth 

 and truncated obliquely at the anterior end, the centre of the trun- 

 cation with a small pyramidal process, which is the extremity of tin- 

 foot. The posterior parts are less muscular, and the termination is 

 usually a funnel-shaped expansion, variously developed in different 

 individuals ; for in some it is firm and well developed, and in others 

 it is scarcely perceptible. This expansion is separated from the rest 

 of the body by a strongly-defined contraction. There is a muscular 

 ring, broader on the ventral than on the dorsal surface, above this 

 contraction, and by that ring the animal is attached to the shell, which 

 on its inner Hurfoce present*, at about one-fifth of its length from the 

 posterior extremity, a corresponding impression in the shape of a 

 horse-shoe, the interrupted portion being ou the concave side. On 

 the dorsal surface a small elevation is perceptible, at about one-third 

 of it* length from the anterior end, indicating the place of the head. 

 The whole extent below this is occupied by two muscles on each side, 

 distinctly observable through the abdominal parietes. These muscles 

 are symmetrical, flattened, and directed obliquely from the sides of 

 the foot toward* the dorsal surface and the posterior extremity of 

 the animal, giving rise to and becoming commingled with the muscle 

 of attachment On the abdominal surface, likewise, there are on each 

 aide, at about one-third of it* length from the anterior end, two 

 symmetrical organs deeply jagged, and of a dark brown colour : these 

 form the liver. Below this point, nearly the whole of the abdomen is 

 visible through it* transparent pariete* filled by granulations con- 

 tained in the very Urge ovary, and by the straight descending intestine 

 which terminate* at the expanded extremity in a mesial vent. The 

 whole of the anterior part of the animal i* invented by a fine mem- 

 brane, which i fixed posteriorly to the origin of the foot, and U free 

 in front, where its circumference i* thickened. It i* perforated in its 

 centre, and M. Iteshayes considers thu to be the mantle. The 

 thickened portion i* produced by a circular sphincter, which, when 

 contracted, wrinkle* the skin, closely embraces in it* opening the 

 extremity of the foot, and thu* cut* off any external communication. 

 M. I/Orbigny, jun., who furnished a drawing of the living animal in 

 an expanded state, make* the dilated lobe* of the foot resemble a 

 flower whose undulated and small corolla support* in it* centra a 

 j.i.til thickened toward* the middle, and pointed at it* free end. 



"n .litting the mantle down the middle of it* dorsal surface 

 separating it from its insertion to the right and left, and turning it 

 downward* and to the right, the foot, the head, and the branchiu; 



Die foot i* elongated, subcyliudrica], slightly conical, and 

 flattened from above downwards, fle*hy throughout, and situated 

 at the interior and anterior part of the head, having its upper 

 and under surfaces slightly grooved in the middle. The anterior 

 extremity i* largest, and iU centre is occupied by a sort of conical 

 miT , broader at iU base, being there partly covered by two small 

 notched lateral lobe., the notches corresponding with the grooves of 

 ' Th. posterior extremity ha* a bifurcated appearance, owing 



to the attachment there of the retractor muscles ; ' 



project* a little into the abdominal cavity, giving support to the 

 stomach and the other principal viscera. 



The head couaist* only of a mouth, and U situated superiorly at 

 the hinder extremity of the foot. It U bell-shaped, and flat 

 from before backwards. Two black |><>iuta ou its side* might be mis- 

 taken for eyes, but these are the jaws situated within the mouth, and 

 visible through the thin substance of which it is composed : they are 

 .spherical, horny, rough on their outer surface, cleft in the miiUi 

 bearing a considerable resemblance to a small bivalve oln-11. Th.-iv 

 are two lips deeply cleft at the margin, or, more properly speaking, 

 furnished each of them with three pairs of labial tentacles, those of 

 the posterior lip, the middle pair especially, being much larger thau 



1. Shell of Dattatium JStiluli>, natural size. 2. Shell mainlined, broken 

 longitudinally, showing the animal In a contracted state; a, the pontcrior 

 extremity prulunging iuelf into a imull accidental tube. 8. Magnified, repre. 

 cntlng toe animal at the moment of It* advancing out of the shell ; a, '., the 

 foot, the lob. of which arc developed in the form of a corolla ; r, a part of the 

 collar. 4. The animal magnified, abdominal aspect ; a, extremity of the foot ; 

 k, the collar ; r, r, the mantle j d, d, the liver ; r, the Intestine ; /, the ovary ; 

 a, the muscle of Insertion ; .;', It, the pavilion and it neck ; i, the vent. 



i i. Magnified, doraal aspect ; a, extremity of the foot ; t, the collar ; r, r, the 

 mantle; d, slight projection produced by the head and the brumhin-; r, r, 

 Internal retractile muscles ; /, /, external retractile mmcle ; jr, neck of the 

 puvlllon ; A, the pavilion. G. Magnified : the mantle hat been |lit in the 

 dorul anil menial line, detached In part from IU jiosterlor insertion, and turned 

 aside showing, a, the extremity of the foot which closes the aperture j, of the 

 collar /, m, of the mantle >i, ", p ; t, t, lobes of the foot ; c, the foot itself, prc. 

 renting a depression or < tunnel running IU whole length ; rf, the head ; f, the 

 cerebral ganglion ; /, /, the two buccal Jaws ; f, f, the pedicle* or branchiferom 

 membrane* ; , , i, i, the branchln ; f. f, (f, ij, the retraetor miiM-les ; , the 

 muscle of liwrrtioii; I, the neck of th.- p.mll.m. 7. fig. 4 natural M/e. 



I 8. flg. 5 natural M/.I-. (IKvliayes.) 



