Part 69

SINUOUS. Winding, serpentine. The septa of Ammonites are sinuous. The muscular impression of the mantle, or palleal impression of some bivalve shells, is sinuated near the posterior muscular impression.

SINUS. (Sinus, a winding, or bay.) A winding or tortuous excavation. The sinus in the outer lip of Strombus, fig. 406; and that in the muscular impression of Venus, will be indicated by the letter s.

SIPHON. ([Greek: Siphon], siphon.) A pipe, or tube. A shelly tube passing through the septa of chambered shells. It is said to be dorsal, central, or ventral, according to its situation near the outer, or inner parts of the whorl. See Introduction.

SIPHONAL SCAR. The name applied by Mr. Gray, to the opening or winding sinus in the palleal impression of a bivalve shell, in the place where the siphonal tube of the animal passes.

SIPHONARIA. Sow. ([Greek: Siphon], siphon.) Fam. Phyllidiana, Lam. Patelloidea, Bl.--Descr. Patelliform, depressed, inclining to oval, ribbed; apex nearly central, obliquely inclining towards the posterior margin; muscular impression partly encircling the central disc, but interrupted in front, where the head of the animal reposes, and at the side by a siphon, or canal passing from the apex to the margin.--Obs. This siphon, which is in some species very distinct, serves to distinguish this genus from Patella. S. Sipho, fig. 231*.

SIPHONOBRANCHIATA. Bl. (Siphon, and Branchiæ, gills.) The first order of Paracephalophora Dioica, Bl. divided into the families Siphonostomata, Entomostomata, and Angiostomata.

SIPHONOSTOMA. Guild. A sub-genus of Pupa, consisting of several elongated species, which have the aperture detached from the whorls; such as P. costata, and fasciata.

SIPHONOSTOMATA. Bl. ([Greek: Siphon], siphon; [Greek: stoma], stoma, mouth.) The first family of Siphonobranchiata, Bl. the shells of which are extremely variable in form, but always have a canal or notch at the anterior extremity of the aperture. This family partly answers to the Canalifera of Lamarck and the genus Murex in the system of Linnæus. It contains the genera Pleurotoma, Rostellaria, Fusus, Pyrula, Fasciolaria, Turbinella, Columbella, Triton, Murex, Ranella, and Struthiolaria.

SIPHUNCLE. (Siphunculus.) A small siphon.

SISTRUM. Montf. RICINULA, Auct. fig. 413.

SKENEA. Flem. A genus including some species of EUOMPHALUS and CIRRUS.

SMILUM. Leach. Fam. Pedunculated Cirripedes.--Descr. Thirteen pieces, ten of which are in pairs, lateral, subtriangular; one posterior dorsal, linear; all smooth; peduncle hairy.--Obs. This genus is distinguished from Pentelasmis, by the number of its valves, and from Scalpellum, by the hairy peduncle. S. Peronii, fig. 36.

SNAIL. The common garden Snail, so destructive to our vegetables, belongs to the genus Helix. The water snail, found in ponds, is Planorbis.

SOL. Humph. A genus consisting of several species of the genus Trochus, and corresponding with the sub-genus Tubicanthus, Sw. Malac. Fig. 349.

SOLARIUM. Auct. (A terrace, or gallery.) Fam. Turbinacea, Lam. Goniostomata, Bl.--Descr. Discoidal beneath, conical above, with a wide umbilicus, the spiral margin of which is angulated and crenulated; aperture trapezoidal; peritreme thin, sharp; columella straight; operculum horny, subspiral.--Obs. The Solarium Perspectivum, is commonly called the Staircase Trochus, from the angulated edges of the whorls being seen through the umbilicus, which reaches to the apex, and presents the appearance of a winding gallery. The species are not numerous, they belong to tropical climates. A few fossil species occur in the tertiary formations. Fig. 353, S. Perspectivum.

SOLDANIA. D'Orb. A genus of microscopic Foraminifera.

SOLEN. Auct. (A kind of shell-fish, Plin.) Fam. Solenacea, Lam. Pyloridea, Bl.--Descr. Bivalve, transversely elongated, sub-cylindrical, equivalve, very inequilateral, gaping at both extremities, umbones terminal, close to the anterior extremity; hinge linear, with several small cardinal teeth, and a long, external ligament; muscular impressions distant, anterior tongue-shaped, placed behind the cardinal teeth, posterior irregular, sub-ovate; palleal impression long, bilobed posteriorly.--Obs. The above description of the genus Solen, is framed so as to admit only those species which are commonly called Razor Shells, with the umbones terminal, and the anterior muscular impression behind them. They are found buried deep in the sand, in a perpendicular position, their situation being pointed out by a dimple, on the surface. They are abundant in temperate climates. Some of the Lamarckian Solenes will be found in the genus Solenocurtus, Bl. Fig. 60, 61.

SOLENACEA. Lam. A family of the order Conchifera, Dimyaria Lam. The shells belonging to it are described as transversely elongated, destitute of accessary pieces, gaping only at the lateral extremities; ligament external.--The genera may be thus distinguished.

1. SOLEN. Razor shells, truncated at the extremities. Fig. 60.

2. PANOPÆA. Broad, with prominent tooth. Fig. 65, 66.

3. SOLENOCURTUS. Rounded at the extremities, with internal bar. Fig. 61.

4. SOLENIMYA. No teeth, epidermis over-reaching the shell. Fig. 68.

5. GLYCIMERIS. Thick, fulcrum of the ligament prominent. Fig. 67.

6. LEPTON. Flat, scale-shaped. Fig 62.

7. NOVACULINA. Umbones nearly central; covered by a thin epidermis. Fig. 63.

8. GLAUCONOME. Oval, margins close. Fig. 64.

SOLENELLA. Sow. (Solen.) Fam. Arcacea, Lam.--Descr. Oval, equivalve, subequilateral, compressed, covered with a thin, shining, olive-green epidermis; hinge with three or four anterior, and numerous sharp posterior lateral teeth, arranged in a straight line; muscular impressions two, lateral; palleal impression with a large sinus; ligament external, prominent, elongated.--Obs. This genus partakes of the characters of the genus Nucula, and of the family Solenacea. A few specimens of the only species known (S. Norrisii, fig. 138.) were dredged by Mr. Cuming at Valparaiso.

SOLENIMYA. Lam. (Solen and Mya.) Fam. Mactracea, Lau. Pyloridea, Bl.--Descr. Equivalve, inequilateral, transversely oblong, rounded at the extremities with the umbones near the posterior side, covered with a shining brown epidermis extending beyond the edges of the shell; hinge without teeth; ligament partly internal, placed in the margin of an oblique, flattish, posterior rib; muscular impressions two, distant, lateral. From the Mediterranean, Australian, and Atlantic Oceans.--Obs. Solenimya differs from Solenocurtus and the true Solens, in having the posterior side of the shell the shortest; in the internal ligament; and in being destitute of teeth. It resembles Glycimeris, but is not incrassated. Fig. 68, Solenimya radiata.