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Show 384 MOLLUSCA. are the eyes. The mouth is a vertical orifice, beneath which is a filament on each side, that has all the appearance of a tentaculum, but belonging in reality to the foot. The branchire form but a single range along the left side of the roof of the branchial cavity. The right side is occupied by the rectum and the spermatic canal, which also transmits the ova. There is no penis, the animal fecundating itself. The species are numerous, but not very distinct. Linnreus left them among the Serpulre( 1 ). The V ERMILIJE, also left by M. de Lamarck near the Serpulre, are 1iimilar to the V ermeti( 2 ). MAGILus, Montf., The Magili have a longitudinally carinated tube, which is at first regularly spiral, and then extends itself in a line more or less straight; although the animal is unknown, it is highly probable that it should be placed near the Vermeti(3). The SILIQUARIA, Brug. Resembles Vermetus in the head, the position of the operculum, and in the tubular and irregular shell; but there is a fissure on the whole length of this shell which follows its contour, a.nd which corresponds to a similar cleft in that part of the mantle which covers the branchial cavity. Along the whole side of this cleft is a branchial comb, com· posed of numerous, loose and tabular-like lamellre. Linnreus left them with the Serpulre, and till very lately they were considered as belonging to the class of the Annelides( 4). (1) Serpulalumbricali3, L., Adans., Senegal, XI, 1, and several new species. (2) Serpula triquetra, Gm., Born., Mus., pl. xviii, t. 14. (3) Magilus antiquus, Montf., II, pl. 43, and Guettard, Mem., III, pl. lxxi, f. 6. (4) Serpula anguina, L.;-Serpula muricata, Born., Mus., XVIll, 16. N.B. M. de Lamarek considered the Siliquarire and the Vermilire as neigh· hours of the Serpulre. M. de Blainville has approximated them to the Vermeti; M. Audouin has lately observed and described the animal, and to him do we owe what is stated above. GASTEIWPODA SCUTillHANCIIIAT A. 385 ORDER VIII. SCUTTBRANCIIIAT A( 1 ). The Scutibranchiata comprjse a certain number of Gasteropoda, similar to the Pectinibranchiata, in the form and position of the branchire, as well as in the general form of the body, but in which the sexes are united, in such ·a way, however, as to allow them to fecundate themselves. Their shells are very open, without an operculum, and most of them without the slightest tnrbination, so that they cover these animals, and particularly their branchim, in the manner of a shield. The heart is traversed by the rectum, and receives the blood from two auricles, as is the case in the greater number of bivalves. The HAt.YOTis, Lin.(~) Is the only genus of this order in which the shell is turbinated; it is distinguished from that kind of shell by the excessive amplitude of the aperture, and the flatness and smallness of the spire, which is seen from within. This form has caused it to be compared to the ear of a quadruped. In the HALYOTIS, Lam-., Or the true Halyotes, the shell is perforated along the side of the columella by a series of holes; when the last hole is not terminated, it gives to that part the look of an emargination. The animal is one of the most highly ornamented of all the Gasteropoda. A double membrane, cut into leaves and furnished with a double range of filaments, extends, at least in the most common species, round the foot and on to the mouth; outside its long tentacula, are two cylindrical pedicles which support the eyes. The mantle is deeply cleft on the right side, and the water, which passes through the shell, penetrates through it into the branchial cavity; along its edges we (l) M:. ue Blainville unites this order and the following one (the Chitones excepted) in his SUb·c}ass of the p ARACEPll.ALOPHORA. HERMAPRRODIT.&. (2) The PARACJ:PHAI.oPH. HEnMAPH. 0Txn., Blainv. Vot. II.-2 y |