46 MOLLUSCA. TBACHELIPODA. 



let bands ; umbilicus deep and narrow ; aperture dilated. 8 lines 

 long. Inhabits European seas. Browns Illust. pi. 45, fig. 5, 8. 

 Shells of the genus Trochus are found in Britain in the inferior oolite, lias, and 

 London clay. See Fleming's British Animals, p. 324. 



Gen. 43. ROTELLA, Lam. Trochus, Lin. 

 Shell orbicular, shining, without epidermis; spire very short, sub- 

 conoid, with the lower surface convex and callous ; aperture 

 semirotund. 



This genus, distinguished by the callosity which covers a great part of the under 

 surface of the shell, and of which the Trochus vestiarius of Linnaeus is the type, are 

 all marine. 



R. lineolata, Lam. (T. vestiarius, Lin.) Shell orbicular, convex-co- 

 noid, very smooth, pale flesh coloured, with crowded longitudinal 

 and waved fuscous lines j whorls contiguous ; lower surface white. 

 Transverse diameter 4 to 7 lines. Inhabits Mediterranean. 

 Bonan. 3. fig. 355. 



Gen. 44. SOLARIUM, Lam. Trochus, Lin. 

 Shell orbicular, in the form of a depressed cone ; umbilicated ; 

 crenulated or dentated in the internal margins of the whorls ; 

 aperture wide ; mouth quadrangular ; no columella. 



The shells of this genus are marine. But few recent species, and not many fossil 

 ones are known. 



S. perspectivum, Lam. Shell convex, yellowish white, with fuscous 

 or chestnut and white bands near the sutures ; umbilicus large, 

 pervious, and elegantly crenulated. 1 to 3 inches broad, and less 

 than half as long. Indian Ocean Lister, pi. 636, fig. 24. 



S. variegatum, Lin. Shell orbicular, convex, transversely sulcated, 

 and longitudinally striated, variegated with white and red ; um- 

 bilicus spreading, crenulated. 8 lines in diameter. Inhabits 



South seas Chem. v. pi. 173, fig. 1708, 1709. 



The fossil British species of this genus are found in the London clay and upper 



oolite. 



FAMILY II. SCALARIDES. 



Shell destitute of plicae or folds at the columella ; margins of 

 the aperture united in a circular form. 



Among the Trachelipoda which respire in water, the Peristomida and the Scalarides 

 are the only groups which have the margins of the opening united. But the former 

 are fluviatile shells, and the present family are marine. In this family also the shell 

 forms but a loose spire, the whorls being often widely separated from one another. 



Gen. 45. DELPHINULA, Lam. Turbo, Lin. 

 Shell subdiscoid or conical, umbilicated, solid, with the whorls 

 of the spire rough or angular ; aperture entire, round, some- 

 times trigonal, with the borders united, generally fringed or 

 furnished with a ridge ; spire depressed. 



The shells of this genus are solid, thick, nacreous interiorly, with the whorls of 

 the spire rough or rugged outwardly, or at least angular at the side of the umbili- 

 cus. There is no apparent pillar. The greater part are rough with spines, branch- 

 ed testaceous fringes, tubercles, or scabrous striae. 



