C Y S 



[ 126 ] 



D A V 



English species are recorded in Mr. 

 Morris's catalogue, one only of 

 which, the C. leeve, belongs to the 

 Silurian system. Lycett. 



CYSTIDEA. The seventh order of 

 the class Echinodermata. All the 

 genera of this class are extinct, 

 and found fossil only. 



CYSTIPHYLLUM. (from /CVST/.S, vesica, 

 and 0vXXoi/, folium, Gr.) A genus 

 of corals found in the Silurian 

 rocks, and thus named by Mr. 

 Lonsdale. Externally, they are 

 striated; internally, composed of 

 small bladder-like cells. From 

 this internal structure, and from 

 the absence of a distinct centre, 



Mr. Lonsdale has named the genus, 

 separating it from the Cyathophylla 

 of Goldfuss. 



CYTHER^J'A. A marine bivalve; equi- 

 valve, lenticular, oval ; hinge with 

 two cardinal teeth ; one anterior 

 lateral tooth in each valve, which 

 distinguishes this genus from Yenus. 

 It is found in depths of the ocean 

 varying to fifty fathoms, in mud 

 and coarse sands. Several species 

 have been found fossil in the ter- 

 tiary deposits. Cytheraea nitidula 

 is mentioned by Dr. Mantell as 

 occurring in the London clay, and 

 cythersea convexa in the Plastic 

 clay. 



D 



DACHSTEIN BEDS. Beds of the triassic 

 period. The Dachstein beds attain 

 in some parts of Germany a thick- 

 ness of 2,000 feet, they are of white 

 or greyish limestone. Below, these 

 beds are unfossiliferous, but above, 

 they contain beds made up of corals. 



DACTYLOPO'BA. A genus of lapideous 

 free polypifers, of a cylindrically 

 elevated form, with a perforation 

 in the narrower extremity. The 

 surface reticulated with rhomboidal 

 meshes, the network itself porous. 



DA'OTJEITE. The siberite of Lermina. 

 A variety of the red shorl of Siberia, 

 called also rubellite. This stone is 

 found in Siberia mixed with white 

 quartz. It is composed of silica 

 56, alumina 36, with some oxide 

 of manganese, and oxide of iron. 

 Daourite is another term for ru- 

 bellite; it is in fact a variety of 

 tourmaline, of a red colour. It 

 has obtained a variety of names, 

 as, rubellite, siberite, daourite, 

 tourmaline, apyre, red schorl of 

 Siberia, &c. See Tourmaline. 



DA'SYPTTS. (SaavTrovs, from a<rt>9 and 

 irovs, Gr.) The armadillo, which 

 seee 



DASYU'KTJS. An animal of the mar- 

 supial order. The dasyurus is said 

 to be the largest of the carnivorous 

 marsupial animals. The head of a 

 species of dasyurus has been dis- 

 covered in the Eocene freshwater 

 limestone of Auvergne. 



Dasyurus ursinus is a very fero- 

 cious creature about the size of a 

 badger, its actions and habits much 

 resemble those of a bear. 



DA'THOLITE. j The Dystom-spath of 



DA'TOLITE. ) Mohs. A sort of 

 spar-stone; the siliceous borate of 

 lime. According to Menil, it is a 

 combination of silica 38 f 50, lime 

 35-60, boracic acid 21-30, water 

 4' 60. Its varieties are named 

 Botryolite, Earthy Botryoidal Da- 

 tolite, and Common Datolite. It 

 has been found principally in 

 Norway, in beds of magnetic iron- 

 ore. 



DA'VYNE. A earthy mineral, de- 



