DEC 



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DEN 



side of the stem, so as to appear to 

 be of one piece with it ; these 

 leaves are called decurrent. 



DECTT'BSIVELY PINNATE. Applied to 

 leaves having their leaflets decur- 

 rent, or running along the petiole. 



DECTJ'SSATE. (decusso, Lat.) To in- 

 tersect at acute angles ; to cross 

 each other at right angles. Ap- 

 plied to branches growing in pairs, 

 and alternately crossing each other 

 at right angles ; applied also to 

 leaves alternately opposite. In 

 conchology, applied to stria3, cros- 

 sing or intersecting each other at 

 acute angles. 



DEFLE'XED. (deflexus, Lat.) In 

 entomology, having the sharp edge 

 bent downwards. 



DIGEADATION. (degradation, Fr. H 

 signifie ddptrissement, etat de dSca- 

 denoe, de ruine. This term is used 

 by geologists to signify the lessen- 

 ing or wearing away of rocks, 

 strata, &c., by the action of water, 

 or other causes. 



DEHI / SCETT. (dehiscent, Lat.) In 

 botany, fruits which open when 

 ripe, so as to enable the seeds 

 to escape, are termed dehiscent. 

 Gaping; opening. 



DELPHI'NULA. (from delphinus, Lat.) 

 A turbinated, subdiscoidal, um- 

 bilicated univalve. The aperture 

 round and pearly; operculum horny. 

 The delphinula creeps on rocks and 

 sea-weeds. This genus is formed 

 of shells formerly included by 

 Linnaeus in his genus Turbo. La- 

 marck places delphinula in the 

 family Scalariana. The fossil del- 

 phinula occurs in the tertiary 

 deposits; it is also recent. 



DE'LTA. A term applied by geologists 

 to the alluvial deposits formed at 

 the mouths of rivers. It has ob- 

 tained its name from a supposed 

 resemblance to the Greek letter A. 

 Deltas are occasionally of immense 

 size, and they are divided into lacus- 

 trine, mediterranean, and oceanic, 

 the first being those formed in lakes, 



as the delta at the mouth of the 

 Rhone, at the upper end of the 

 lake of Geneva; the second, or 

 mediterranean, are those formed in 

 inland seas, as that at the mouth 

 of the Rhone, where it enters 

 the Mediterranean; the third, or 

 oceanic, are those formed on the 

 borders of the ocean, as the delta 

 of the Ganges. 



DELTHY'EIS LIMESTONE. A shaly 

 limestone, met with in the Heidel- 

 berg group. 



DE'LTOID. (from delta, the fourth 

 letter of the Greek alphabet.) The 

 name of a muscle of the shoulder, 

 from its supposed resemblance to 

 the Greek letter A ; triangular. 



DE'NDRACHATE. (from SevSpov and 

 a^ar^s, Gr.) An agate with delin- 

 eations of trees, ferns, moss, &c. 

 Some of these are exceedingly 

 beautiful, and are so elegantly 

 depicted that they have been erro- 

 neously taken for real plants, whence 

 their name. These pebbles are 

 found abundantly on the shore from 

 Bognor to Brighton, and, when cut 

 and polished, are made into very 

 beautiful necklaces, brooches, snuff 

 boxes, &c., &c. 



DE'NDRITE. (Sevtyi, Gr.) The 

 same as dendrachate. 



DENDK'ITE AGATE. A species of agate, 

 thus named from its containing in 

 its interior brown, reddish-brown, 

 or blackish delineations of leafless 

 trees, shruhs, &c. For a descrip- 

 tion see Mocha stone. 



DENDEI'TICAL. Containing the re- 

 semblance of trees, ferns, or mosses. 



DENDR'ODUS. In the transverse 

 section of these reptile teeth the 

 cancelli are found to radiate from 

 the open centre towards the cir- 

 cumference, like the spokes of a 

 wheel from the nave ; and each spoke 

 seems as if it had sprouted into 

 branch and blossom, presenting the 

 appearance of a well-trained wall- 

 tree: hence the generic name 

 Dendrodus, assigned by Professor 



