714 



tractile motion of the abdominal rings ; thus a roof 

 is by degrees formed, the particles of which are glued 

 together, so that at length a covering, or umbrella, 

 sufficiently large to conceal the entire body of the 

 tender larva is produced, it is of course subject to 

 the motions of the fork by which it is supported, so 

 that it is sometimes even carried perpendicularly. 

 As, however, this parasol would in time become 

 unwieldy, we find this inconvenience provided against 

 by the casting of the entire skin, not onjy of the body, 

 but also that of the various spines, as well as of the 

 supporting fork. This takes place several times pre- 

 vious to the larvae being transformed into pupae. It 

 is a difficult operation, and at the period of the last 

 moulting, i. e. on becoming pupae, the tails are com- 

 pletely lost. It is upon the same leaf that the larvae 

 has to undergo these moultings as well as to assume 

 its quiescent form. To prepare itself for this, it 

 ceases to hold the tail either in a raised or recumbent 

 position upon the back, but, on the contrary, stretches 

 it out behind in the same line as the body. It 

 attaches itself to the leaf by the two segments which 

 follow the last pair of legs ; the skin then breaks behind 

 the head, and by degrees is sloughed entirely off, having 

 previously remained tranquil for two or three days. 

 The exuviae, however, remain for some time at the 

 extremity of the body, which has caused incautious 

 observers to state that the pupa is furnished with two 

 prongs as well as the larva. The pupa is flat, nearly 

 oval, with the head concealed beneath the thorax, 

 which is very large, and of a semi-kmar shape in front, 

 being bordered with spines. This portion of the 

 body has been incorrectly figured by Reaumur as 

 divided by a slit down the middle, it is, however 

 entire: the abdominal portion is also bordered by 

 large leaf-like appendages of a flat shape, and pointed 

 at the sides and tip. The pupa is green, and in the 

 underside of the body are clearly to be observed the 

 antennae, legs, and other parts of the perfect insect, 

 which makes its appearance at the end of fifteen or 

 twenty days after the larva sheds its last skin. 



The females lay their eggs upon the leaves of 

 various plants, as thistles, burdock, &c., arranging 

 them side by side, and forming them into patches 

 often covered with excrement. 



The genus cassida is the only indigenous group 

 belonging to this tribe, there being nearly twenty 

 species, most of which are, however, rare. The Cassida 

 cquestria of Fabricius is one of the largest and most 

 common example. 



CASSIDARIA (Lamarck). This genus of mol- 

 luscs must certainly be considered very nearly allied 

 to the genus Cassis; a separation is however neces- 

 sary, from some manifest differences of character 

 The shell is generally more inflated and rounder than 

 those of the Cassis, and a very marked distinction 

 is observable in the canal which terminates the lower 

 part of the aperture. This, in the Cassidaria, is ascen- 

 dent, and very little arched (while in the Cassis that 

 part is abruptly recurved towards the back of the 

 shell) ; the spire is short, conoid, composed of convex 

 whorls, without any thickened bands ; the left margin 

 apparent and affixed to the columella, which is mos 

 generall}' covered with small rough, oblong, trans 

 verse tubercles; right lip plaited or thickened 

 exterior tranversely grooved, and the upper part o 

 the whorls, in some species, regularly dotted wit! 

 round tubercles. They have a horny oncrculurn, and 

 are found in the seas of warm latitudes ; seven o 



C ASS I BAR I A CASSIS. 



jight species are known; that figured here is the 

 C. echinophora, and strongly defines the peculiarities 



Cassidaria echinophora. 



of the genus. They are thus subdivided : 1st, The 

 oval sub-globular species, with the canal sub-ascen- 

 dant; and 2nd, The oblong sub-cylindrical species, 

 with a very short straight canal, forming Sowerby's 

 genus Oniscia. De Blainville places this mollusc in 

 ris second class Paraccphalophora ; first order, Sipho- 

 nobranchiata ; second family Entomostomata. The 

 animal, according to Adanson, is the same as that of 

 the Purpura and its congeners. Several fossil species 

 are known. 



CASSIS (Lamarck). A genus of molluscs neces- 

 sarily separated from the Linnaean genus Buccimini, 

 in which the notch at the base is but slightly defined, 

 compared with the canal at the base of shells of this 

 genus, which is lengthened and abruptly turned to- 

 wards the back ; the form of the aperture is also 

 very distinct, being longitudinal, straight, and nearly 

 always dentated on the right side, the flattened side 

 of the columella lip forming a very considerable angle, 

 the spire seldom much elevated, frequently inter- 

 rupted by thickened bands, or varies obliquely, having 

 formed so many terminations or lips of the previous 

 stages of growth, and constituting the discriminating 

 character of the first section of the genus ; the second 

 not possessing these bands, the general form of these 

 shells is inflated, the columella plaited or wrinkled 

 transversely, the exterior smooth or nodulous, and the 

 spire with bands or nodules only. They sometimes 

 attain a great size ; and in one species the columella 

 lip projects above the spire, giving a flat ovate-an- 

 gular appearance to the lower surface of the shell. 

 They have a horny operculum, and are marine shells, 

 inhabiting principally the Indian seas : nearly thirty 

 species are known ; two or three of which are how- 

 ever found in the Mediterranean. Several fossil 

 species are described ; that figured here is the C. 

 tubcrosa, internal portions of which, as well as of the 



Cassis hiberosa. 



other species, are exquisitely sculptured by Italian 

 artists in imitation of antique cameo gems, the dif- 

 ferent strata of colouring matter resembling those of 

 the onyx and other precious stones. Of these a 



