E P 



[ 399 ] 



SEE 



rying from a few inches to a foot in 

 diameter, and divided into cells or 

 chambers of irregular form ; some- 

 times they are nodules of clay, 

 having the chambers filled with 

 spar; they are usually found, in 

 argillaceous strata. Masses of ar- 

 gillaceous limestone, traversed in- 

 teriorly by cracks passing in 

 different directions, and containing 

 calcareous spar. Septaria were at 

 one time considered to be confined to 

 the London clay deposit, and to be 

 characteristic of it, but subsequent 

 discoveries have proved the in- 

 correctness of that opinion. 



SE'PTHM:. (septum, Lat.) A partition. 

 The plates dividing the chambers 

 of multilocular shells are termed 

 septa; a partition separating cer- 

 tain portions of the brain is called 

 the septum ; and the cartilaginous 

 partition of the nostrils is called 

 the septum of the nose. 



SE'EAPHIM. The name given by the 

 workmen to impressions of a sort 

 of fossil lobster or gigantic crus- 

 tacean in the old red sandstone. 



SE'BOLIS. A genus of crustaceans, 

 affording the nearest approach 

 among living animals to the ex- 

 ternal form of the trilobite. The 

 greatest difference between the 

 serolis and trilobite consists in the 

 former possessing a fully developed 

 series of crustaceous legs and 

 antennae, whilst the trilobite does 

 not display any traces of either of 

 these organs. 



SE'BPENTINE. A mineral substance 

 deriving its name from its spots 

 and variegated colours, supposed 

 to resemble the skin of the serpent ; 

 its colours and their peculiar ar- 

 rangement are in great measure 

 characteristic. It sometimes forms 

 whole rocks. It differs from horn- 

 blende in containing a larger por- 

 tion of magnesia and a smaller 

 quantity of iron. There is, how- 

 ever, an intimate connection be- 

 tween serpentine and hornblende, 



as the latter is observed, in some 

 situations, to be changed into ser- 

 pentine by contact with limestone. 

 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 3-5, water 10-5, 

 oxide of iron 4-5 = 101. There 

 are two varieties, the precious and 

 the common serpentine. When 

 serpentine is found intermixed 

 with patches of crystalline white 

 marble, it constitutes a stone deno- 

 minated verde antique. Some crys- 

 tallised varieties have obtained the 

 name of diallage, or Schiller spar. 



SE'BPTTLA. A genus of the order 

 Tubicola, class Annulata. The 

 animal a terebella ; shell univalve, 

 tubular, generally adhering to 

 other substance; often separated 

 internally by septa at uncertain 

 distances. Serpulas are generally 

 littoral, attached to rocks, stones, 

 shells, crustaceans, corals, and 

 other marine bodies; sometimes 

 several species are found on one 

 stone or shell. Scapulae may com- 

 monly 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. 



SEBPULI'NA. An order of the anne- 

 lida of MacLeay, who thus describes 

 them " sedentary animals without 

 eyes or antennae. They live in 

 tubes which are either a natural 

 transudation of their body, and are 

 membranaceous or calcareous, or 

 the tubes are semifactitious, compo- 

 sed of agglutinations of sand, &c." 



SEBPULI'TES LONGI'SSIMUS. The name 

 assigned by Sir K. Murchison to a 

 fossil shell of the Upper Ludlow 

 Rock. The following description 

 is taken from his Silurian System. 

 " Very long, hardly diminishing 

 in diameter, compressed, smooth, 



