300 



DENTALIUM. 



DENTEX. 



310 



those of the anterior. There is a naked space in the centre of the 

 anterior lip indicating the aperture of the mouth, which is con- 

 tracted into a short fleshy oesophagus, terminating rapidly in a thick 

 pear-shaped stomach, supported by and closely adhering to the 

 extremity of the foot, and containing within, near the cardiac opening, 

 a rather complicated tooth-like apparatus. By a distinct vessel from 

 each of the symmetrical lobes of the liver its secretion is poured into 

 the stomach, which terminates below in a slender, transparent, straight, 

 mesial intestine, opening, as before observed, at the dilated posterior 

 extremity. 



The heart is symmetrical, situated above the stomach, and con- 

 tained in a pear-shaped pericardium. A vascular trunk issues from 

 the anterior extremity of this sac, passes in the direction of the neck, 

 and divides into two large branches, one being distributed to each of 

 the branchias. 



The branchiae two, symmetrically situated on the lateral and pos- 

 terior parts of the neck, and supported on a divided pedicle or bran- 

 chiferous membrane, formed of many very fine soft flexible tenta- 

 cular filaments with club-shaped terminations, and appearing from 

 their position to be equally adapted for directing nourishment 

 towards the mouth, and for fulfilling their important office of aerating 

 the blood. 



The nervous system is apparently ganglionic ; the cerebral ganglion, 

 the only one yet detected, is small, quadrilateral, considerably elon- 

 gated, and placed longitudinally on the middle of the posterior 

 surface of the head. Two very minute filaments issue from its 

 inferior angles and pass to the oesophagus ; they have not been traced 

 beyond it. 



M. de Blainville (' Malaeologie,' 1825) agrees with M. Deshayes in 

 the conclusion to which the latter came, namely, that Denialium is 

 a true Mollusk, and he makes it the type of his first order Cirrlto- 

 branchiata, of his first section of hia third sub-class, Paracephalopftora 

 Hermaphrodita, placing it next to Patella. M. Rang (1 829) follows 

 De Blainville in referring it to his order Cirrhobranchiata, of which 

 Kang makes it the only family, as does De Blainville, and he gives it a 

 situation between Pitturella and Patella. Cuvier, in the last edition 

 of the ' Regne Animal ' (1830), still retains Dentalium among the 

 Aiiin''lMi"<, placing it immediately after f>iphoitoma of Otto; but he 

 adds, that the recent observations of Savigny, and above all those of 

 Deshayes, render such a classification very doubtful. The animal, he 

 observes, does not appear to possess any sensible articulation, nor any 

 lateral hairs (soies), but it has anteriorly (en avant) a membranous 

 tube, in the interior of which is a sort of foot, or fleshy and conical 

 operculum, which closes its orifice. On the base of this foot, he adds, 

 is a small and flattened head, and on the nape are to be seen the 

 plumose branchiae. If, be continues, the operculum recals to mind 

 the foot of the Vermtti and Siliquarite, which have already been trans- 

 ferred to the class of mollusks, the bronchia; remind us of Amp/iitrite 

 and Tcrcbellum ; and he concludes by remarking that ulterior obser- 

 vations on their anatomy, and principally on their nervous and 

 vascular systems, will resolve this problem. Dr. J. E. Gray, who has 

 compared the description of the animal given by M. Deshayes with 

 specimens in the British Museum, is, he informs us, satisfied with 

 the correctness of that description, and he considers that the most 

 natural situation of Dentalium is nearest the Fimurelloe, but still far 

 from them. The apices of the British species, he observes, often 

 appear to be either broken off, or to have fallen off of themselves, like 

 the tips of decollated shells ; and he adds, that when the tip is broken, 

 the animal forms a slight tube within, which is more or less produced 

 beyond the tip ; and that the late Dr. Turton described a specimen 

 in this state as a species under the name of D. labiatum. Dr. Gray 

 thinks that there is only one species found on our coasts, the other 

 so-called species being mere varieties depending either on the worn or 

 broken state of the specimens. . In his ' Spicilegia Zoologica ' he has 

 described a Fiphunculiu which inhabits these shells, and which, he 

 believes, has been considered by some authors to be the real inhabitant 

 of the fhe'l. 



The geographical distribution of the genus is very much 

 extended ; few seas are without some of the species, which vary 

 much in size. They are found sometimes in deep water, fre- 

 quently near the shore. Professor E. Forbes has dredged the 

 British species I). Knlalii and J). Tarentinvm at from ten to fifty 

 fathoms' depth. About 30 recent species have been described, and 

 70 fossil. 



M. Deshayes separates his species into four groups : 



1. . 

 Shell not slit at its posterior extremity. 



a. Longitudinal stria;. 



Example, D. ElephaiUinum, 



b. No longitudinal stria;. 



Example, D. Entalii. 



2. 



Shell nlit at its posterior extremity. 



n. Longitiulin.il striae. 



Example, // tlrialum. 



b. No longitudinal striri'. 



Example, D. eburneum. 



Shell having a marginal rim ; not slit at its posterior extremity. 

 Example, D. strangulatum. 



Fossil Dentalia. 



" Of fossil species," says Mr. G. B. Sowerby, " there are many, par- 

 ticularly in the marine beds of the Tertiary Formations ; the London 

 Clay and the Calcaire Grossier swarm with several sorts not easily 

 distinguishable from the recent species, among which we may particu- 

 larly remark the fossil species from Piacenza, which so nearly resembles 

 D. Elephantinum that Brocchi has not hesitated to refer it to that 

 species, and the D. eburneum of Lamarck, which he says inhabits 

 India, and is found fossil at Grignon. Deshayes in his ' Tables' gives 

 the number of living species as 23, of the fossil (tertiary) 34, and the 

 following, D. Elephaniinum, D. deMalis, D. novem costatitm, D. Entalix, 

 D. eburneum, D. fi&sura, and D. strangulatum, as both living and fossil. 

 Mr. Mautell in his tabular arrangement of the organic remains of the 

 county of Sussex ('Geol. Trans.' vol. iii., second series, 1829), notes a 

 species, which he does not name, in the blue clay of Bracjdesham ; 

 D. planum, in the arenaceous limestone or sandstone of Bognor ; 

 D. cylindricum, in the sand on Emsworth Common ; D. atnatitm, 

 D. elliplicum, and D. decnsiatmn, in the Gault, or Folkstone marl ; and 

 one or more, unnamed, in the Shanklin sand (Lower Greensand). 

 Dr. Fittou figures one species, V. medium, from the Greensand of 

 Blackdown, in his interesting ' Observations on some of the Strata 

 between the Chalk and Oxford Oolite in the South-East of England.' 

 ('Geol. Trans.' vol. iv., second series, 1836.) And he notes D. ellip- 

 ticum in the Gault at Copt Point, on the authority of the Rev. G. E. 

 Smith. In his ' Systematic and Stratigraphieal List of Fossils ' four 

 named species, including D. ellipticum,- D. medium, and an uncertain 

 species, are noted from the Gault of Kent, South Wilts, and Cambridge, 

 and the sands of Blackdowu. Dr. Lea, in his ' Contributions to Geo- 

 logy ' (1833), describes two new species, D. alteiiiatum and D. tuwitum, 

 from the Tertiary Beds of Claiborne, Alabama, and gives the following 

 summary : ' In Great Britain 1 4 species have been obtained from 

 the Lias to the Crag. M. Deshayes's 'Tables' give 84, of which 13 are 

 from the Paris basin, the Eocene period. In this country (America) 

 Dr. Morton has observed casts in the Upper Greensand of New Jersey 

 and Delaware ; and Mr. Say one species, the D. aitenuatum, in the 

 Tertiary of Maryland.' " 



DENTA'RIA, a genus of Plants belonging to the natural order 

 Cntciferce, the sub-order Siliqitosfe, and the tribe Arabidece. It has a 

 lanceolate compressed pod, flat nerveless valves, a capitate stigma; 

 the seeds in a single row, the funiculus dilated, winged. 



D. btilbifera, the Coralwort, is the only British species of this 

 genus. It has a simple stem, alternate leaves, the lower leaves 

 pinnate, the upper leaves simple, the axils of the leaves producing 

 bulbs. It has a thick fleshy rhizoma with tooth-like knobs, hence 

 its name. The flowers are rose-coloured or purple. It is a rare 

 plant in England, but it is found in the neighbourhood of Tunbridge 

 Wells. 



(Babington, Manual of Britiih Botany.) 



DENTATI. [AMMONITKS.] 



DENTEX, a genus of Fishes belonging to the family Sparidce. 

 It has the following characters : Body deep, compressed ; dorsal fin 

 single ; head large ; teeth conical, placed in a single row, four in 

 the front above and below elongated, and curved inwards, forming 

 hooks; teeth on the branchial arches, but none on the vomer or 

 palatine bones ; nose and suborbital space without scales ; branehi- 

 ostegous rays 6. There are several species of this genus. 



D. rulijarit, the Four-Toothed Sparus, is regarded as a native of 

 England. Only one specimen however seems to have been taken in 

 this country, and that by Mr. Donovan in 1805 off Hastings. It is 

 a very common fish in the Mediterranean, and is the Dentex of the 

 Romans. It is remarkable for the great length of the four anterior 

 teeth in each jaw. It acquires sometimes a large size weighing from 

 20 to 30 pounds, and measuring 3 feet jn length. Mr. Donovan's 

 specimen weighed 16 pounds. "A more voracious fish," says Mr. 

 Donovan, " is scarcely known ; and when we consider its ferocious 

 inclination and the strength of its formidable canine teeth, we must 

 be fully sensible of the great ability it possesses in attacking other 

 fishes even of superior size, with advantage. It is asserted, that 

 when taken in the fisherman's nets, it will seize upon the other 

 fishes taken with it, and mangle them dreadfully. Being a swift 

 swimmer it finds abundant prey, and soon attains to a consider- 

 able size. Willughby observes that small fishes of this species are 

 rarely taken, and the same circumstance has been mentioned by later 

 writers. During the winter it prefers deep waters, but in the spring 

 or about May it quits this retreat, and approaches the entrance of 

 great rivers, where it deposits its spawn between the crevices of stones 

 and rocks. 



"The fisheries for this kind of Spanu are carried on upon an 

 extensive scale in the warmer parts of Europe. In the actuaries of 

 Dalmatia and the Levant, the capture of this fish is an object of 

 material consideration, both to the inhabitants generally as a whole- 

 some and palatable food when fresh, and to the mercantile interests 

 of those countries as an article of commerce. They prepare the fish 

 according to ancient custom, by cutting it in pieces and packing it in 



