R H A 



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ROC 



RHACHEOSAO'RUS. A fossil saurian of the 

 lias and oolite. 



RHA'TIZIT. The name given by Werner to 

 prismatic kyanite. 



RHINO'CEROS. (pivoKepotg, Gr. from piv, 

 a nose, and ictpas, a horn : rhinoceros, 

 tat. rhinoceros, Fr. rinoceronte, It.) A 

 genus of thick-skinned mammalia, in- 

 cluded by Cuvier in the family Pachyder- 

 rnata Ordinaria. The rhinoceros is found 

 at the present day, in India, Java, Africa, 

 and Sumatra. It is a large animal, hav- 

 ing three toes, but the feet not cloven. 

 The bones of the nose support a solid horn 

 in two species of this genus ; but the other 

 species possess two horns. Burchel and 

 Campbell met with more than one new 

 species of rhinoceros in their journey from 

 the Cape of Good Hope into the interior. 

 Campbell's had a straight horn projecting 

 three feet from the forehead, different from 

 any he had before seen, its horn resem- 

 bling that of the supposed unicorn. Rev. 

 W. Kirby. 



Fossil remains of the rhinoceros are 

 found in Siberia and Germany. The en- 

 tire carcass of a fossil rhinoceros was 

 discovered, in frozen sand, on the banks 

 of the Wilaji, in Siberia. Bones and 

 teeth of the rhinoceros are found in this 

 country in superficial gravel and loam. 



RHIPI'PTERA. A new order of insects, 

 established by Mr. Kirby under the name 

 of Strepsiptera (twisted wings), named 

 Rhipiptera by Latreille, includes only 

 two genera, namely, stylops and xenos. 

 These insects are remarkable for their 

 anomalous form, and the irregularity of 

 their habits. The tegmina are fixed at the 

 base of the anterior legs ; they are both 

 long and narrow, and appear to be in- 

 capable of protecting the wings. The wings 

 are large, membranous, divided by longi- 

 tudinal and radiating nervures, and fold 

 longitudinally, after the manner of a fan. 



RHIZO'MA. (piZwfta, a root, Gr.) A 

 species of creeping stem which grows 

 under-ground. 



RHIZO'PODES. The name proposed, by M. 

 Dujardin, to a new class of animals of 

 lower degree than the radiata, possessing 

 a power of locomotion by means of minute 

 tentacular filaments. This new class 

 would comprise the animals which con- 

 struct the miliola, and some microscopic 

 foraminiferous shells. 



RHOMB. (po/z/3oc, Gr. rhombus, Lat. 

 rhombe, Fr. rombo, It.) In geometry, 

 an oblique angled parallelogram, or qua- 

 drilateral figure, whose sides are equal 

 and parallel, but the angles unequal, two 

 of the opposite sides being obtuse, and 

 two acute. 



RHO'MBIC. Having the figure of a i*homb. 



RHO'MBOID. (from popflog, a rhomb, and 



e7^oc, form, Gr.) Is a figure which has 

 its opposite sides equal to one another, 

 but all its sides are not equal, nor are its 

 angles right angles. 



RHOMBO'IDAL. Having the form of a 

 rhomboid. 



RHO'MBUS. A rhomb ; that which has its 

 sides equal, but its angles are not right 

 angles. 



RHOMB SPAR. Called also bitter spar, a 

 variety of magnesian carbonate of lime. 

 This variety occurs crystallized, most of 

 its crystals being rhombs, sometimes 

 truncated, and sometimes with rounded 

 edges. Fracture foliated, the foliae having 

 a shining or splendent lustre, more pearly 

 than that of calcareous spar. Specific 

 gravity from 2*48 to 3'00. It is gene- 

 rally of a greyish colour to pale yellow, or 

 yellowish brown. It appears to pass by 

 imperceptible shades into dolomite. 



RI'BBED. 



1. Having bones communicating with and 

 attached to the vertebrae, and serving to 

 protect the organs contained within the 

 chest. 



2. In botany, a term applied to leaves 

 when they possess large raised vessels on 

 the under side. 



3. In conchology, when shells have ridges, 

 or ribs, either longitudinal or transverse. 



RI'MA. In conchology, the interstice be- 

 tween the valves, when the hymen is 

 removed. 



RI'NGENT. (from ringo, to grin, Lat.) 

 In botany, applied to a monopetalous co- 

 rolla, the border of which is usually 

 divided into two lips, which gape like the 

 mouth of an animal. A corolla with two 

 lips is called bilabiate ; when these pre- 

 sent an appearance like the mouth of 

 an animal, the corolla is called ringent. 



ROCK, (roc and roche, Fr. rocca, It.) 

 Rocks, and the substances they enclose, 

 lie beneath the superficial accumulations, 

 and constitute the crust of the earth. 

 The term "rocks" is apt to mislead 

 beginners ; for under this title geologists 

 rank clay, sand, coal, and chalk, as well 

 as limestone, granite, slate, and basalt, 

 and other hard and solid masses, to which 

 the use of the term is generally restricted. 

 -Prof. Phillips. 



The rocks of which the mineral crust 

 of the globe is composed are divided into 

 those of aqueous and igneous origin, 

 from the two agents known to us as 

 capable of their production. Rocks are 

 also divided into primary, transition, se- 

 condary and tertiary. These, and many 

 other divisions, such as crystalline, fos- 

 siliferous, &c. &c. are described in the 

 various works on geology. 



ROCK BU'TTER. Native alum. It occurs 

 in the cavities or fissures of argillaceous 



