SUB-BIVALVES. A term of distinction applied by De Blainville, to those spiral univalves which have an operculum; these, as they constitute two distinct pieces, he considers as forming a medium between univalves and bivalves. SUB-MYTILACEA. Bl. The sixth family of the order Lamellibranchiata, Bl. the shells belonging to which are described as free, rather pearly, regular, equivalve; hinge dorsal, laminated; ligament external; two muscular impressions; palleal impression not sinuated. This family, with the exception of the last genus, agrees with the family Nayades of Lamarck, and contains the genera Anodon, Unio, and Cardita. SUB-OSTRACEA. Bl. The second family of Lamellibranchiata, Bl. the shells of which are described as of a compact texture, sub-symmetrical; with the hinge rather complex; one single, sub-central, muscular impression, without any traces of palleal impression. This family corresponds with the Pectenides of Lamarck, and part of the genus Ostrea in the system of Linnæus. It contains the genera Spondylus, Plicatula, Hinnites, Pecten, Pedum, Lima. SUB-SPIRAL. Not sufficiently spiral to form a complete volution. SUBULA. Bl. (_An awl._) A generic name under which M. De Blainville includes TEREBRA maculata, Auct. f. 428, together with nearly all the species of Terebra, enumerated by Lamarck and other authors; only leaving in the latter genus those species, which being more bulbous, or ventricose, nearly resemble Buccinum in general form. These last mentioned species, such as Terebra buccinoidea, (fig. 247) have been formed into a new genus by Mr. Gray, under the name Bullia. If both these genera were adopted, the genus Terebra would be extinct. SUBULATE. (_Subula_, an awl.) A term applied to shells which are long and pointed as in Terebra. Fig. 427, 428. SUCCINEA. Drap. (_Succinum_, amber.) _Fam._ Colimacea, Lam. Limacinea, Bl. _Sub-genus_, Cochlohydra, Fer.--_Descr._ Ovate, rather elongated; aperture large, entire, longitudinal; spire short; outer lip thin, continuous with the thin, sharp-edged columella; inner lip spread over a part of the body-whorl.--_Obs._ The shells belonging to this genus of partly amphibious mollusca, are distinguished from Limnæa by not having a fold on the columella The S. amphibia is of a bright amber colour. Fig. 265, 266. Temperate and tropical climates. SULCATED. (SULCATUS, lat.) Having grooves or furrows. SULCI. Grooves or furrows.