RISSOA. 95 



and Rack. Trans. Linn. Soc. vol. viii. p. 162. — Turt. 

 Conch. Diction, p. 201. — Dillw. Recent Shells, vol. ii. 

 p. 837.— Wood. Index Testae, pi. 30, f. 50. 

 Ciiifjula striata, Fleming, Brit. Animals, p. 307. — Brit. Marino Conch, p. 1")J, 



f. 99 (not well). 

 Rissoa minuiissima, Michaud, Nouv. Esp. de Riss. p. 20, fig. 27, 28. — Desh. 

 Anim. s. Vert. vol. viii. p. 480, — Potiez and Mich. Gal. 

 Douai, Moll. vol. i. p. 274 — Recluz, Revue Zool. Cuvier. 

 1843, p. 6. 

 „ comnmnis, Forbes, Malacol. Monensis, p. 17. 



„ senate, (not Quoy, nor Desh.) Johnston, Berwick. Club, \o\.\. p. 271 

 (with animal). — Macgilliv. Moll. Aberdeen, p. 152. 

 Cinffula seimcoslata, Fh^Mit^i}, Brit. Animals, p. 307. — Brit. Marine Conch. 



p. 177. 

 liissoa f/racilis, Macgill. Moll. Aberd. p. 152, from which Ciiyula (jracilis, 

 Brit. Mar. Conch, p. 202 ; copied also. Brown, lllust. Conch. 

 G. B. p. 129. 

 Oilostomia semicodaia, Macgill. Moll. Aberd. p. 155. 



„ Mariouis, Macgill. Moll. Aberd. p. 156 (teste Jeffr. from type); 

 copied, Brit. Mar. Conch, p. 260, and Brown, 111. Conch. 

 G. B. p. 1 30. 

 Itissoa decussata. Brown, lllust. Conch. G. B. 

 Pyramis candidus and discors. Brown, lllust. Conch. G. B. p. 14, pi. 9, f. 31, 



32. 

 Rissoa semicot-tata. Brown, 111. Conch. G. B. p. 11, pi. 9, f. 1, 2. 



The very different look of the adult and immature 

 individuals of this most abundant shell, induced Montagu 

 to regard the latter as a distinct species, which he pub- 

 lished under the name of T. semicostatus. The 0. Mariona 

 of Macgillivray is the same in a rather more advanced 

 stage, the relative proportions of the spire and month 

 varying of course with age, and especially in this Rissoa, 

 whose penult turn is nearly as large as the final volu- 

 tion. The B, gracilis of the same author was also de- 

 rived, observes Mr. Jeffreys, after an inspection of the 

 type, from a slender worn specimen of this species. 



The form of this shell, although varying greatly as to 

 elongation, is always remarkably narrow, being cylindra- 

 ceous below, and convexly tapering above. Characteristic 



