258 sinuous. 



orbicular, 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 Linnaeus, from which, however, it is distinguished by 

 the longitudinal slit, fig. 1 . S. anguina. The recent species are 

 found in the sponges with siliceous spiculse, in the Mediter- 

 ranean ; the fossils in tertiary beds. 

 SIMPLE. (Simplex, lat.) Single, entire, uninterrupted, un- 

 divided. 

 SIMPLEGAS. Mont. 1, 83. (Simplex, simple ; yaarrip, (/aster, 

 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. 

 SJNUOUS. Winding, serpentine. The septa of Ammonites are 



