CIRCULUS-NORRISIA. 275 



Valvata striata Phil., Enum. Moll. Sicil., i, p. 147, t. 9, f. 3 (1836). 

 — Adeorbis striatus Searles Wood, Crag Mollusca, p. 137, t. xv, f. 

 7. — Chenu, Manuel, i, p. 352, figs. 2589, 2590. — Adeorbis striatus 

 Phil. Tasle, Catal. Morbihan, p. 36. — Cyclostrema striata Phil. Petit, 

 Catal. Test. Mar., p. Ill (1S69).— Cyclostrema striatum Phil. Fischer, 

 Actes Soc. Linn. Bord. 1869, p. 129. — Granger, Moll, de France, 

 p. 142 (1885). — Skenea striata Phil. Arad. et Ben. Conch, viv. 

 mar. della Sic, p. 158 (1S70).— Cir cuius striattis Phil. Monterosato, 

 Not. int. alle Conch. Medit., p. 31 (1872); Nuova Revista, p. 23; 

 Enuiu. e Sinon., p. 20. — ^Fischer, Brach. et Moll, du litt. oc. de 

 France, p, 13 (1878). — Jeffreys, Proc. Zool. Soc. Lond., 1883, p. 

 95. — BucQUOY, Dautzenberg and Dollfus, Moll. Mar, du 

 Roussillon, p. 420, t. 51, f. 1, 2, 3 (1886). — Delphinula duminyi 

 Requien, Coq. de Corse, p. 64 (1848). — Trochus (Circulus) diiminyi 

 Req. Jeffreys, Brit. Conch, iii, p. 315 ; v, p. 203, t. 62, f. 5 (1865). 

 — Trochus duminyi Req. Weinkauff, Conchyl. des Mittelmeeres, 

 ii, p. 374. — Skeneia striatida Weinkauff, Journ. de Conchyl. 1862, 

 p. 343. — Delphinula costata Danilo et Sandri. Elenco nomin., p. 

 123 (1856). 



This tiny shell has much the appearance of a Cyclostrema ; from 

 which genus, however, the 10 or 12 whorled corneous operculum and 

 slightly nacreous interior separate it. The authors of " Les Mollus- 

 ques du Roussillon " give as measurements, alt. 2, diam. 4 mill. ! which 

 is enormously larger than any I have seen, the largest of which is 

 only 2h mill, in diam. The species is found living from the littoral 

 zone to considerable depths. It is found fossil in the pliocene (Crag) 

 of England, and in Italy. The fossil forms described by Searles 

 Wood as Adeorbis supranitidus and tricarinatus (Crag Moll., p. 137, 

 138, t. XV, f. 5, 6) are evidently closely allied. Solarium philijjjiii 

 Cantraine is also said to be synonymous. 



The discoidal form, strong spiral ridges of the upper surface and 

 concave smooth base, discontinuous peristome, etc., render the species 

 easily separable from other known recent forms. 



Genus NORRISIA Bayle, 1880. 



Norrisia Bayle, Journ. de Conchyl. 1880, p. 241. — Fischer, 

 Manuel de Conchyl., p. 825. — Trochiscus Sowerby, Ann. and Mag. 

 N. H. 1838, p. 96; and of most authors, not Trochiscus V. Heyden, 

 Isis, 1826, a genus of Arachnida, nor Trochiscus Held, 1837, a sec- 

 tion of Helices. 



