168 



CREPIDULINA CRICETUS. 



in being apparently constantly fixed to one spot, as 

 the form of their base assumes the shape of the sub- 

 stance to which they adhere ; an examination of the 

 animal, however, clearly distinguishes the genera. 

 The shell is an oval or oblong, with a much depressed 

 concave exterior, the spire inclined obliquely to one 

 side, the margin entire, and the opening partially 

 closed horizontally by a partition, giving it the 

 appearance of a half-decked boat; some have angular 

 longitudinal ribs on the surface, others have them 

 armed with spines or prickles ; they never possess 

 an operculum, which marks a strong distinction be- 

 tween them and the Navicula, The portion of testa- 

 ceous matter, partly closing the aperture, is placed 

 between the mass of the animal's viscera and the 

 posterior part of its foot. The muscular impression 

 is in the form of a horse-shoe. A very natural associa- 

 tion of species will be found as follows : such as have 

 the shell thick, quite flat, and the summit not spiral, 

 as in the C. porcellana, the next being nearly of the 

 same form, but very thin and with an epidermis, and 

 the last such as are nearly round, C. garnotus, and 

 the summit subspiral, C. subspirata. 



There are probably ten or twelve species described 

 and about six fossil; they are of the second class 

 Paracephalophora, third order Scutibranchiata, second 

 family Calyptracea. 



CREPIDULINA (Blainville ; CRISTELLAJUA, 

 Lamarck). All the shells of this genus were united 

 by Lamarck in his genus Cristellaria. The greater 

 number of them are microscopic, and figured and 

 described by Fichtel, who devoted much time and 

 attention to these minute molluscs. The shell is oval, 

 lengthened, a very small spiral summit ; the last turn 

 very ample, oval, nearly straight through its whole 

 length, and closed by a diaphragm of the same form. 

 The Nautilus planntus may be considered the type of 

 the genus. Interesting as these small shells doubtless 

 are, as illustrative of the connecting link in the great 

 chain of relationship between the molluscous animals, 

 and important as they must ever be as exhibiting in 

 miniature all the same parts and functions as shells do 

 of a gigantic structure, they nevertheless will only be 

 valued by those who are anxious to investigate nature \ 

 under every difficulty, and generally speaking to little 

 advantage, since where one species admits of being 

 seen by the power of ordinary optical instruments, 

 there are thousands that are never seen at all but by 

 the use of the most costly microscopes. 



CREPIS (Willdenow). A genus of herbaceous 

 uncultivated plants, mostly annuals, and mostly 

 natives of Europe. The flowers are yellow, a good 

 deal like those of the hawkweed, of course they belong 

 to the natural order Composite. 



CRESCENTIA (Linnaeus). A genus of West 

 Indian trees remarkable for their large fruit. LinnEean 

 class and order Didynamia Angiospennia, and natural 

 order Solancee, Generic character: calyx in two 

 parts, equal, deciduous ; corolla, bell-shaped, bellying, 

 limb two lipped, and of four or five lobes, upper lip 

 short and crenated ; stamens, rudiments of five ; 

 anthers two-lobed ; style bearing a bilamellated 

 stigma ; fruit like a gourd, large, one-celled, many- 

 seeded, no placenta ; seeds compressed and round. 

 This is called the calabash tree in the West Indies ; 

 the shell of the fruit being made into various kinds of 

 vessels. The plants are in our collections, and chiefly 

 valued for their fine foliage. They may be propa- 

 gated by cuttings struck in moist heat. 



CREUSIA(Leach). These molluscs, like the genus 

 Pyrgnma of Dr. Leach, are th only two genera known 

 to possess four valves, and the operculum to consist, of 

 two pieces only. Linnaeus classed them with his genus 

 Lepaa. They are in general small shells, affixed to 

 madrepore or other marine substances, of an orbicular 

 or conical convex form, composed of four unequal 

 valves united, but distinctly marked by a suture at the 

 divisions, the operculum bivalve and internal ; a con- 

 siderable calcareous support penetrating the substance 

 to which the animal attaches itself. They belong to 

 the family Jial-anitlcx, and the animal partakes of the 

 same functions. All the species of this family are so 

 extremely singular and interesting, that it is much to 

 be wished some naturalist, within reach of observing 

 them in a living state, would direct his attention to a 

 careful examination of these animals. In our opinion 

 it would throw a very important light on the organi- 

 sation of other molluscs, and those imperceptible gra- 

 dations of change, so remarkable and so unaccountable 

 in their structure, many of which may certainly be 

 traced to necessity, but what has created that neces- 

 sity, at present remains a mystery. 



CRICETUS, hamster, a genus of rodent mam- 

 malia, resembling the rats in some particulars, but 

 differing from them in many others. Their teeth are 

 nearly the same, but their tail is short and covered 

 with short hair, and their mouths are furnished with 

 cheek pouches, in which they can carry a store of 

 provisions to their subterranean retreat. The charac- 

 ters of this genus are : larger than the rat ; reddish grey 

 above ; black in the flanks and underneath, with three 

 white spots on each side ; its fore feet arc white, and 

 there is also a white spot under the throat, and another 

 under the chest. There are some individuals entirely 

 black. This animal, so agreeably varied in colour, is 

 one of the most hurtful which exists, in consequence 

 of the quantity of grain which it gathers, and with 

 which it fills its holes, which are at times nearly seven 

 feet in depth. 



The hamster is confined to the northern parts of 

 the eastern world, and is most abundant in those 

 places which bear a resemblance to the extensive 

 plains to the westward of Rio de la Plata, in South 

 America. In Europe, it is not found to the westward 

 of the Rhine, but in proportion as the sandy plains 

 are approached, it becomes more numerous. One 

 can easily understand why this should be the case ; 

 and that it should be so, is a very wise provision of 

 nature ; for were hamsters abundant in the most fer- 

 tile parts of the world, in those which are best adapted 

 for cultivation, and, therefore, most valuable to man, 

 such places would soon be rendered desolate, so 

 rapidly do these animals increase in number, and 

 so great are the ravages which they commit. 



In a state of nature, the hamster partakes not a 

 little of the ferocious disposition of the rat ; and it has 

 been alleged, that when in a state of confinement they 

 have been known to prey upon each other, as is done 

 by rats, moles, and some other burrowing animals. 

 Still, however, the principal part of its food consists 

 of vegetable matter, a store of which is laid up for at 

 least part of the inclement half of the year, though the 

 probability is that it hybernates the other half. It digs 

 with great facility ; each burrow it forms is composed 

 of two entrances, one which conducts to an oblique 

 canal, at the entrance of which the animal throws out 

 and accumulates the earth which it is forced to re- 

 move, the other which serves as an exit to a vertical 



