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series of crustaceous legs and antennse, 

 whilst the trilobite does not display any 

 traces of either of these organs. Captain 

 King has lately collected many specimens 

 of scrolls on the east coast of Patagonia, 

 and in the Straits of Magelhaens he saw 

 the beach covered with them dead. Prof. 

 Buckland. 



SE'RPENTINE. A mineral substance de- 

 riving its name from its spots and varie- 

 gated colours, supposed to resemble the 

 skin of the serpent ; its colours and their 

 peculiar arrangement, are in great measure, 

 characteristic. It sometimes forms whole 

 rocks. It differs from hornblende in con- 

 taining a larger"" portion of magnesia and 

 a smaller quantity of iron. There is, 

 however, an intimate connection between 

 serpentine and hornblende, as the latter 

 is observed, in some situations, to be 

 changed into serpentine by contact with 

 limestone. The grain of serpentine is 



fine, and its texture compact : it may be 

 cut or scraped with a knife, but it does 

 not yield to the finger-nail. When broken, 

 it possesses some lustre and a slightly 

 unctuous feel. Its surface, which is 

 sometimes glossy, is soft to the touch. 

 Specific gravity from 2-5 to 2*7. Before 

 the blow-pipe it hardens but does not 

 fuse. Its constituents are magnesia 34-5, 

 silex 28-0, alumine 23'0, lime 0-5, water 

 10-5, oxide of iron 4-5 = 101. There are 

 two varieties, the precious and the com- 

 mon serpentine. When serpentine is 

 found intermixed with patches of crystal- 

 line white marble, it constitutes a stone 

 denominated verde-antique. Some crys- 

 tallized varieties have obtained the name 

 of diallage, or schillar spar. Many of the 

 Alpine districts of Europe contain beds 

 and rocks of serpentine ; but Patrin states 

 that there is no serpentine in Northern 

 Asia, neither was any seen in the Andes 

 of South America, by Humboldt. In the 

 United States it is met with abundantly. 

 Brongniart has given to serpentine the 

 name of Ophiolite. In the Apennines, the 

 serpentine rests upon saussurite, the 

 saussurite upon jasper, and the jasper 

 upon limestone. Its degree of hardness, 

 and the peculiar arrangement of its co- 

 lours form the distinctive characters of 

 serpentine. BaJcewell. Cleaveland. 



SE'RPULA. A genus of the order Tubicola, 

 class Annulata. The animal a terebella ; 

 shell univalve, tubular, generally adher- 

 ing to other substances ; often separated 

 internally by septa at uncertain dis- 

 tances. Serpulse have only been found 

 to inhabit the ocean. They are generally 

 littoral, attached to rocks, stones, shells, 

 crustaceans, corals, and other marine bo- 

 dies ; sometimes several species are found 

 on one stone or shell. In Turton's Linne 



forty-eight species of serpula are de- 

 scribed, twenty-seven of which inhabit 

 the seas of our coasts. Serpulse may 

 commonly be seen upon the shells of 

 lobsters, crabs, oysters, &c., to which 

 they adhere by the lower surface, looking 

 like small worms creeping upon them. 

 Wherever the sea is or has been, they 

 abound either in a recent or fossil 

 state. 



SE'RRATE. } (serratus, Lat. from serro, to 

 SE'RRATED. ji saw.) Jagged; notched. 



1. In botany, applied to leaves, the mar- 

 gins of which resemble a saw, the teeth 

 pointing towards the extremity of the 

 leaf. 



2. In entomology, applied to the bodies 

 of insects, the margins having jagged in- 

 cisions, like the teeth of a saw. 



SE'RRULATE. } (from serrula, a little saw, 



SE'RRULATED. $ Lat.) When the edges 

 of leaves or margins of shells are very 

 finely jagged or notched, they are said 

 to be serrulated, and not serrated. 



SERTULA'RIA. A genus of ai'borescent 

 corals belonging to the family Tubu- 

 larii. 



SE'RUM. (serum, Lat , serum, Fr.) The 

 thin, watery, transparent part of the 

 blood. 



SE'SAMOID. (from (reader], an Indian 

 grain, and dSog, resemblance, Gr. sesa- 

 mo'ide, Fr.) The name of some exceed- 

 ingly small bones found at the root of the 

 thumb or great-toe. 



Sfi'saui. (A contraction of semisque, Lat. 

 signifying and a half. ) A prefix to many 

 words, signifying the quantity and a half 

 more. 



SE'SSILE. (from sessilis, seated, Lat.) In 

 botany, applied to flowers when placed 

 directly on the branch or stem ; also to 

 leaves when they grow directly from the 

 stem, branch or root, without any foot- 

 stalk : any part of a plant which com- 

 monly is borne on a stalk, is said to be 

 sessile when it has none. 



SETA'CEOUS. (from seta, a bristle, Lat.) 

 Bristle-shaped ; bristly. 



SHALE, (schale, Germ.) Slate clay ; in- 

 durated slaty clay. 



SHA'NKLIN SAND. Called also lower 

 green sand. A marine deposit of sili- 

 ceous sands and sandstone of various 

 shades of green, red, brown, yellow, feru- 

 ginous, grey, and white, with subordi- 

 nate beds of cherts and siliceous lime- 

 stones, constitute the formation called 

 the Shanklin sand, or lower green 

 sand. It is the lowest member of the 

 cretaceous group, intervening between the 

 gault above and the weald clay below. 

 The beds consist of an aggregation of 

 sand, with comminuted shells and frag- 

 ments of corals, impregnated with iron, 



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