CUE 



C 



from any of the recent shells, than, 

 the fossil crenatula" It is very 

 rarely found. 



CRENELLA. A genus of bivalve con- 

 ehifera belonging to Lamarck's 

 family Arcacea, and established by 

 Brown. 



CRE'NULATE. } (crenele, Fr.) Indent- 



CRE'NTJLATED. ) ed round the mar- 

 gin with small notches. The fine 

 saw-like edge of the shell of the 

 cockle, which so nicely fits into 

 the opposite shell, is a familiar 

 example of a crenulated margin. 



CRETA'CEOUS GROUP. This group com- 

 prises the different strata from the 

 chalk of Maestricht to the lower 

 green-sand inclusive. In LyelPs 

 Principles, they are thus arranged : 

 1. Maestricht beds ; 2. Chalk with 

 flints; 3. Chalk without flints ; 4. 

 Upper green sand; 5. Gault; 6. 

 Lower green -sand. The whole of 

 these formations are marine. 



The cretaceous group are also 

 divided into Upper Cretaceous, 

 comprising the Maestricht and 

 Faxoe beds; white chalk, with 

 flints ; white chalk, without flints ; 

 chalk marl; upper green-sand; 

 and the gault ; and lower creta- 

 ceous or Neocomian, comprising 

 the lower greensand, the Speeton 

 clay, and the Wealden Beds. 



CRI'CHTONITE. The name given to a 

 black, opaque, shining mineral, 

 after Dr. Crichton. 



CRIO'CERATES. A genus of ammonites, 

 having the whorls disconnected. 



CRINO'IDAL. Containing fossil cri- 

 no'idean remains. The Derbyshire 

 encrinital marble is composed prin- 

 cipally of the fossilized remains of 

 crino'idea, cemented together by 

 carbonate of lime. 



Although the representatives of 

 crinoi'deans in our modern seas are 

 of rare occurrence, this family was 

 of vast numerical importance among 

 the earliest inhabitants of the 

 ancient deep. The extensive range 

 which it formerly occupied among 



the earliest inhabitants of our 

 planet, may be estimated from the 

 fact, that the crinoi'deans already 

 discovered have been arranged in 

 four divisions, comprising nine 

 genera, most of them containing 

 several species, and each individual 

 exhibiting, in every one of its 

 many thousand component little 

 bones, or ossicula, a mechanism 

 which shows them all to have 

 formed parts of a well- contrived 

 and delicate mechanical instrument. 

 Prof. Bucldand. 



CRINO'IDEA. (from icplvov and efo?, 

 Gr.) "I have derived the name 

 of this family," says Miller, "from 

 the Greek -ra gwa Kpivoeidea, the 

 lily-shaped animals, and have used 

 this word, with another distin- 

 guishing term prefixed, to form 

 the name of the genera." Lily- 

 shaped zoophytes. In the most 

 modern classification, Crino'idea con- 

 stitutes the fifth order of the class 

 Echinodermata, and is divided into 

 seven families. A name given to the 

 whole class of encrinites and pen- 

 tacrinites, from their resemblance 

 to the head of the lily. " Of more 

 than thirty species of Crinoi'deans," 

 says Prof. Buckland, "that pre- 

 vailed to such enormous extent in 

 the transition period, nearly all 

 became extinct before the deposition 

 of the Lias. We may judge of the 

 degree to which the individuals of 

 these species multiplied among the 

 first inhabitants of the sea, from 

 the countless myriads of their 

 petrified remains which fill so 

 many limestone beds of the tran- 

 sition formations, and compose vast 

 strata of entrochal marble, extend- 

 ing over large tracts of country in 

 Europe and America." 



The fossil remains of this order 

 have been long known by the name 

 of stone lilies, or encrinites, and 

 have lately been classed under a 

 separate order by the name of Cri- 

 no'idea. This order comprehends 



