CRAT.EVA CREPIDULA. 



167 



in bloom arc most attractive objects. The fruit of some 

 of the species, as the azarole, are esteemed in the 

 dessert in the south of Europe, and many are cultivated 

 as ornamental plants in shrubberies. The common 

 sorts are propagated by seeds, the ornamental species 

 bv gvat'tiiis: on the common. 



CRATJBVA (Linnaeus). A genus of East and 

 West Indian ornamental trees. The fruit of one 

 species in the West Indies is called the garlic pear, 

 from some similar quality. Linmean class and order 

 l}odccandria Monogynia, and natural order Cajyparideee. 

 Generic character : calyx of four sepals, deciduous ; 

 petals clawed, limb often deflexed ; stamens inserted 

 in a glandular disk surrounding the germen ; filaments 

 very long ; anthers linear, and somewhat curved, 

 margined at the base ; germen on a long footstalk ; 

 style none; stigma sitting; berry many-seeded. 

 These plants are kept in our stoves; thrive best in 

 u rich soil, and are propagated by cuttings. 



CRATERINA(Olfers; STENEPTEKYX, Leach). A 

 curious genus of dipterous insects belonging to the 

 section Pupipara (or the order Omaloptfra of Leach), 

 and family Hippoboscidce, or spider flies, and dis- 

 tinguished from Hippobosca by having the wings 

 very long, and so narrow that it seems impossible 

 that they can be employed by the insect as. organs 

 of locomotion. This family o f ' insects is very curious 

 both in their habits and structure. The females, 

 instead of laying their eggs in the usual manner, 

 retain them within the body, not only until the 

 larva is hatched, but also until it has attained its 

 pupa form, in which state it is deposited by the 

 parent fly. These insects are parasitic upon various 

 animals. The only species, however, of which the 

 present genus is composed (Hippobotca Hirundirus, 

 Linuams), infests the swallow, arid, from its large size 

 and the number of individuals sometimes observed 

 upon a single bird, it is evident that they cannot be 

 otherwise than exceedingly troublesome, and even 

 dangerous to this poor bird. The structure of the 

 mouth is very remarkable ; it is formed for suction, 

 and comprises several acute bristles. 



The nests of the swallow are also equally infested, 

 the insects sucking the young birds as soon as 

 hatched. 



CRAY FISH. A crustaceous animal, belonging 

 to the order Decapoda, and section Macroura, and 

 forming the genus Potamobius of Leach, although 

 Desmarets and others unite it with the lobster in the 

 genus Astacns. See ASTACID^E. An idea of this 

 animal may be obtained from our figure. 



Cray-fish. 



^ The cray fish is found in the fresh waters of 

 Europe and the north of Asia. It. secretes itself 

 under stones and in holes in the banks, from which 

 it only comes forth to take its food, which consists of 

 molluscous animals, small fishes, and decaying animal 

 matter. It is said to attain to the age" of twenty 



years, its size gradually increasing all the time, as 

 each year, at the end of the spring, it sheds its outer 

 covering, shonly after which it is found encased in a 

 fresh coat as firm as the old one, and much enlarged, 

 sometimes having increased as much as one-fifth in 

 its size. 



The female deposits her eggs two months after 

 impregnation, these she retains for a considerable 

 time beneath her abdomen, keeping them in such 

 situation by means of a viscid matter with which 

 they are covered, and by which they are attached to 

 the false, or swimming legs, with which this part of 

 the body is furnished in its under surface. These 

 eggs, increase in size before the exclusion of the 

 young, and are exceedingly numerous. The young 

 ones, when hatched, are extremely soft and small, 

 and entirely resemble their parent, beneath the 

 abdomen of which they shelter themselves for 

 several days. The flesh of this auimal is much 

 relished, and various medical properties have been 

 attributed to it, which it is very questionable if it 

 really possesses. It has been remarked, that those 

 which are caught in clear and running streams are of 

 a better taste than those found in stagnant waters 

 and in lakes. They are caught by sinking a net, or 

 spiny faggots, in the middle of "which a piece of 

 putrid meat is placed. We well remember the 

 delight with which, in our schoolboy days, we could 

 escape the trammels of Bonnycastle and Virgil, and 

 go groping, with our shirt-sleeves tucked up, in the 

 holes in brooks where the cray fish were met with, 

 and can therefore speak from experience of the 

 sharpness of the bite which they can inflict with 

 their claws. The tops of their claws were, in bygone 

 times, employed in medicine, being considered as a 

 valuable absorbent when pounded. Their place is 

 now supplied in our pharmacopoeias by the carbonate 

 of magnesia. 



CREN ATUL A (Lamarck ; OSTREA PICTA, Gmel.). 

 This mollusc constitutes a very remarkable genus, 

 somewhat resembling the Myttius, but by the great 

 similarity of the hinge it seems more nearly allied to 

 the Perna. There is, however, even here a distinct 

 and peculiar difference ; the hinge of the crenatula is 

 composed of slightly concave callous crenulations, 

 whence its name. These receive the ligament, while 

 in the Perna the hinge consists of parallel truncated 

 linear teeth, or rather rib-like joints corresponding 

 and opposed to the opposite ones, the ligament being 

 inserted only at their interstices. Shells of this genus 

 are thin and extremely delicate ; of a foliated texture, 

 resembling the Placuna, Avicula, and similarly con- 

 structed molluscs, more or less irregularly formed ; 

 the valves are flattened, foliaceous, and no distinct 

 opening for the byssus ; the summits anterior, gaping 

 backward ; one muscular impression only, which is 

 subcentrical. 



The animal is not yet described, but it properly 

 differs but little from that of the Perna, which must 

 be considered its immediate congener by analogous 

 reasoning ; seven or eight species are known \n the 

 different seas of hot countries, but the most part are 

 found in Australasia. 



De Blainville classes it in the third class Acepha- 

 lophura, third order Lamcllibranchiata, first family 

 Oatracea. 



CREPIDULA (Lamarck; PATELLA, Limneus). 

 This shell is one of the number of those confounded 

 by Linnaeus with the Patella, which it only resembles 



