282 SPONDTLUS, 



SPIEOLOCULINA. D'Orb. A genus of microscopic Forami- 



nifera. 

 SPIE.OEBIS. Lam. A genus composed of a species of Seepula, 

 Auct. wMch are coiled round in a spiral disc like a snake at 

 rest. S. nautiloides is tke common little white shell, found 

 upon the shell of lobsters. PI. i. fig. 5. 

 SPIE/TJLA. {Spira, a winding compass.) Fam. Lituolata, Lam. 

 Lituacea, Bl. — Descr. Convolute, smooth, symmetrical, discoid, 

 with parallel unconnected whorls, divided into numerous 

 chambers by transverse septa ; siphon continuous. — Obs. This 

 pretty little shell is partly internal, only a part of it being 

 visible when on the animal. PI. xxii. fig. 471. 

 S PISTIL A. Gray. A genus composed of Mactea fragilis, and 

 other similar species, which have the ligament sub-external, 

 marginal, not separate from the cartilage ; with the posterior 

 lateral teeth double in one valve, and single in the other. 

 M. fragilis is the species figured for Spisula in Mr. Gray's paper 

 on the MactradsB, in the second series of Loudon's Magazine of 

 Natural History. We have since learned, however, that it 

 was figured there by mistake, not having been intended for a 

 Spisula, but belonging more properly to the genus Mactra, 

 as defined by Mr. Gray, whose description of Spisula, is as 

 follows : — " Shell ovate, trigonal, sub-angular at each end. 

 Hinge and lateral teeth as in Mactra, but hinge of left tooth 

 small. Siphonal inflexion ovate." The principal difference 

 between Spisula and Mactra is, that the ligament is not sepa- 

 rated from the cartilage in the former. M. fragilis, PL iv. 

 fig. 80. 

 SPO]S"DTLTJS. Auct. {A shell-fish, Ancients.) Fam. Pectenides, 

 Lam. Sub-ostracea, Bl, — Descr, Liequivalve, sub-equilateral, 

 irregularly foliaceous and spinose, auriculated, dentictdated at 

 the margins, attached by the lower and deeper valve ; hinge 

 rectilinear, with two prominent teeth in each valve, locking into 

 corresponding cavities in the opposite valve ; umbones separated 

 by a broad, elongated, triangular disc in the lower valve ; liga- 

 ment contained in a groove, dividing the triangular area in the 



