Part 68

5. SPIROGLYPHUS, which hollows a bed in the body to which it is attached. Fig. 8.

Sowerby. (Genera of Shells, published at 50, Great Russell Street, Bloomsbury,) gives satisfactory reasons for re-uniting the whole of the preceding under the name SERPULA.

6. MAGILUS, which burrows in coral; outer lip reflected. Fig. 9 to 10.

7. LEPTOCONCHUS, outer lip reflected. Fig. 11.

8. STYLIFER, spiral, thin, globular, living in Starfish. Fig. 12, 13.

The three last genera should certainly find some other place in the system.

SESSILE CIRRIPEDES. Lam. (Sessilis, low, dwarfish.) An order of Cirripedes, consisting of those which are attached by the base of the shells, containing the genera Tubicinella, Balanus, Coronula, Acasta, Pyrgoma, Creusia. To which may be added some other genera enumerated in explanation of figures 14 to 33. The shells of the Sessile Cirripedes consist of two different sets of valves: 1st. The parietal valves, or pieces arranged in a circle, side by side, around the body of the animal, (an arrangement designated coronular by De Blainville.) 2nd. The opercular valves, or pieces placed so as to enclose the aperture. Between those opercular valves the ciliæ protrude which characterize the class. Besides these two sets of valves, there is generally a shelly plate, serving as a sort of foundation to the rest. The Sessile Cirripedes may be thus arranged.

1. TUBICINELLA. Six parietal valves, tube-shaped, opercular valves perpendicular. Fig. 14.

2. CORONULA. Six parietal valves, opercular valves horizontal. Fig. 15, 16, 17, 18.

These two genera fix themselves in the skin of the Whale. The latter has been divided into the genera Chelonobia, Cetopirus, Diadema, and Chthalamus.

3. PLATYLEPAS. Valves divided, each having a prominent internal plate. Fig. 19.

4. CLITIA. Parietal valves four, opercular valves two, valves dove-tailed into each other. Fig. 20.

5. ELMINEUS. Parietal valves four, opercular valves four. Fig. 22.

6. CONIA. Parietal valves four, thick and porous at the base. Fig. 21.

7. OCTOMERIS. Parietal valves eight. Fig. 24.

8. CATOPHRAGMUS. Parietal valves numerous, irregular. Fig. 23.

9. BALANUS. Parietal valves six; opercular valves four, placed against each other conically in pairs. This genus has been divided into Acasta, Conoplea, Chirona, and Balanus. Fig. 25, 26, 27.

10. CREUSIA. Parietal valves four, supported on the edge of a funnel-shaped cavity. Fig. 28.

11. PYRGOMA. Paries simple, supported on a cavity. This genus has been divided into the genera Nobia, Savignium, Pyrgoma, Adna, Megatrema, and Daracia. Fig. 29 to 33.

SETIFEROUS. Hairy.

SHANK SHELL. The vulgar name for the shell designated Murex Rapa. It is used in Ceylon for ornamental purposes.

SIDEROLITES. Montf. A genus of microscopic Foraminifera.

SIGARETUS. Lam. Fam. Macrostomata, Lam.--Descr. Suborbicular, oblique, haliotoid, thick; spire depressed, consisting of two or three rapidly increasing whorls; aperture wide, entire, modified by the last whorl, the width exceeding the length; columella tortuous; inner lip spread thinly over part of the body whorl; epidermis thin.--Obs. This genus is distinguished from Natica, by the width of the aperture, and the absence of the umbilical callosity. It may be known from Stomatia, and Stomatella, by the texture, which in Sigaretus, is never pearly as in Stomatia, the former being partly an internal shell. Fig. 334, S. concavus. Mostly brought from tropical climates.

SILIQUA. Megerle. (A husk, or pod.) LEGUMINARIA, Schum. A genus composed of species of SOLEN, Auct. which have an internal rib. Fig. 51, Solen radiatus.

SILIQUARIA. Brug. Fam. Cricostomata, Bl. Dorsalia, Lam.--Descr. Tubular, rugose, spiral near the apex, irregularly twisted near the aperture, with a longitudinal fissure radiating from the apex, and proceeding through all the whorls and sinuosities of the tube.--Obs. This genus was included in Serpula by Linnæus, from which, however, it is distinguished by the longitudinal slit, fig. 1. S. anguina. The recent species are found in the sponges with siliceous spiculæ, in the Mediterranean; the fossils in tertiary beds.

SIMPLE. (Simplex, lat.) Single, entire, uninterrupted, undivided.

SIMPLEGAS. Mont. 1, 83. (Simplex, simple; [Greek: gastêr], gaster, belly.) A genus described by De Blainville, as being discoidal, and having the spire uncovered like AMMONITES, but having the chambers divided, by simple septa, like Nautilus.--Obs. The septa of the shell named Simplegas by De Montfort, are evidently sinuous, according to his figure. Fig. 475, S. sulcata.

SINISTRAL. (Sinister, left.) On the left side. A sinistral shell is a reversed one. The sinistral valve of a bivalve shell may be known, by placing the shell, with its ligamentary or posterior part towards the observer; the sides of the shell will then correspond with his right and left side.