438 PLIOCENE MOLLUSCA. 



Genvs TURRITELLA, Lamarck, 1799. 

 Turritella tricarinata (Brocchi). Plate XLIV, figs. 7 — 9. 



1814. Turin* tricarinatus, Brocchi, Conch, foss. subap., vol. ii, p. 374, pi. vi, fig. 21. 



1873-6. Turritella tricarinata, Seguenza, Boll. B. Com. Geol. Ital., vol. iv, p. 356, no. 335, 1873 ; 



vol. v, p. 282, no. 121, 1874 ; vol. vii, p. 100, no. 636, 1876. 

 1880. Turritella communis, var. ariesensis (pt.), Fontannes, Moll, plioc. Vallee <lu Bhone, vol. i, p. 199, 



pi. xi, fig. 4. 

 1882. Turritella tricarinata, von Koenen, Nord-deutsch. Mioc. Moll.-fauna, pt. ii, p. 283, no. 188. 

 1885. Turritella terebra, Lorie, Arch. Mus. Teyler [2], vol. ii, pp. 185, 230, pi. vii, fig. 4. 

 1889-95. Turritella tricarinata, Sacco, Boll. Soc. Geol. Ital., vol. viii, p. 353, no. 1901, 1889 ; Moll. 



Terr. Terz. Piern., pt. xix, p. 5, pi. i, figs. 14 — 19, 1895. 

 1907. Turritella tricarinata, Ravn, Kongl. Dansk Vid. Selsk. Skrift., vol. vii, p. 296, pi. iii, fig. 16. 

 1912. Turritella tricarinata, Cerulli-Irelli, Palaeont. Ital., vol. xviii, p. 158, pi. xxiv, figs. 20 — 25. 



1912. Turritella tricarinata, Cossmann, Ess. Paleoconch. coinpar., vol. ix, p. 112. 



1913. Turritella tricarinata, Grignoux, Ann. Univ. Lyon, n. s. [1], vol. xxxvi, p. 551. 



Specific Characters. — Shell turreted, subulate, smaller and more delicate than 

 T. incrassata ; whorls about 10, decidedly convex ; ornamented by three acute, 

 distinct, and nearly equidistant spiral ridges, the middle one being the strongest 

 and most prominent, with finer lines between them ; spire elongate, slender, 

 ending in a fine point; suture deep and well marked; mouth rounded. 



Dimensions. — L. 30 mm. B. 10 mm. 



Distribution. — Not known living. 



Fossil : Coralline Crag : abundant. Waltonian : Walton-on-Naze, 

 Beaumont, Little Oakley. Newbournian : Waldringfield, probably elsewhere. 



Miocene : Denmark, north Germany, Italy. 



Lower Pliocene : Italy — Ligurian coast, Piedmont. 



Upper Pliocene : Bologna, Monte Mario, Piedmont, Liguria, Altavilla, Dutch 

 borings. 



Pleistocene : Monte Pellegrino, Ficarazzi, Reggio, Naso, Bologna. 



Remarks. — The present Crag form, which appears to correspond with the Italian 

 fossil T. tricarinata, has not been reported hitherto from the Anglo-Belgian basin. 

 Its occurrence at the Coralline and "Waltonian horizons, especially at Oakley where 

 I have found it in great abundance, leads me to think that it has been overlooked 

 by collectors, probably under the impression that specimens of it were dwarf or 

 immature forms of T. incrassata. The latter, however, belongs to a different 

 group, the sub-genus 'Hniishitnr described below. The sculpture of T. tricarinata, 

 moreover, is different; it is a smaller and more delicate shell than T. incrassata, 

 allied to the recent British T. communis. Some authorities consider the latter 

 identical with it, others that the two are varieties of one species. For reasons 

 given in the following section I prefer to regard them as specifically distinct, not 



