History of British animals - University of Guam Marine Laboratory

232 MOLLUSCA. CEPHALOPODA. Rotalia.Gen. IV. ROTALIA.— The lower disc occupied bythe lastformed whorl, the partitions of which radiate from thecentre to the margin ; the whorls on the upperdisc exposed.11. R. Beccaria.— Chambers nearly flat, numerous, the whorlsdextral.N. spiralis, umbilicatus, geniculis insculptis, Walk. Test. Miu. t. iii. f. 63.— N. Bee. Mont. Test. Brit. 186. t. xviii. f. 4 On fuci and corallines.Volutions four or five, forming, above, a slightly convex disc ;the partitionssunk, and convex on the sides ; aperture ovate, transverse near the innermargin: the rays of the partitions of the lower disc obscure towards thecentre.12. R. Beccarii-iperyersus.— Chambers nearly flat, numerous,the whorls sinistral.N. B-p. Walk. Test. Min. t. iii. f. 6. Mont. Test. Brit. 187- t. xviii.f. 6.This shell is found along with the last, and is said by Montaguto beequally plentiful. On the Scottish coast it is greatly more abundant, andgrows to a superior size.13. R. hvflata.— Chambers tumid, few.Naut. inflatus, Mont. Test. Brit. Supp. 81. t. xviii. f. 3 Among sand,Devonshire.Volutions three, the last having five ventricose articulations. The upperdisc is more tumid, and the chambers less crowded than in either of the precedingspecies. In a single specimen found on corallines, Zetland, which Ipossess, the whorls are sinistral, though in other respects it agrees with thedescription of Montagu.Gen. V.LOBATULA.— The upper disc occupied bythe lastformed whorl, the partitions of which radiate from thecentre to the margin ; the whorls on the lower disc exposed.14. L. vulgaris.— Surface of the chambers frosted ; five orsix on the upper disc.N. spiralis, lobatus, anfractibus supra rotundatis subtus depressioribus,Walk. Test, Min. t. iii. f. 71.— Serpula lobata, Mont. Test. Brit. 515.—On shells and corallines, common.Upper disc convex, the partitions and centre slightly depressed, the chambersa little rounded. Lower disc uneven, conforming to the body on whichit rests or adheres ;of three whorls ;aperture at the inner margin, transverse,and nearest the lower disc. A variety, with the whorls sinistral, occursin nearly equal abundance. Both are subject to great variations ofgrowth.