66 FOSSIL MOLLUSCA OF THE CHALK. 



exposed, the upper one being covered by the next whorl ; the tubercles are so placed as to 

 appear to form sloping, transverse bands across the whorls : section of the whorls somewhat 

 rhomboidal : septa, and position of the siphuncle, unknown. 



Spiral angle about 35°. 



Diameter of the largest specimens from Chardstock, in Mr. Wiest's collection, 3 inches. 



This is a well-marked shell, which can hardly be confounded with any other species. 

 We have not met with any specimen turned to the right like that figured by M. D'Orbigny, 

 t, 143, %. 6. 



Abundant in the Chalk with green grains, at Chardstock. (Mr Wiest.) 



7. Turrilites Bechii, S/iarpe. Plate XXVI, fig. 13. 



T. testa turritd, sinistrorsd: anfractibus paucioribus, extra rotundatis, costatis, tubercu- 

 latisque : costis numerosis, svperioribus, Jlexuosis, tenuibus, infra inierruptis : tuber cults 

 biserialibus, inferioribus, numero costarum aqualibus : anr/ulo spirali 30°. 



Shell turreted, sinistral, with a spiral angle of 20° : whorls few, externally rounded, 

 prettily ornamented with numerous delicate, flexuous ribs, which extend from the suture 

 across the upper two thirds of the whorl, where they are interrupted by a smooth space, 

 in which are two rows of tubercles, elongated in the direction of the suture, and equal in 

 number to the ribs ; below these the ribs appear again, bending backwards over the lower 

 side of the whorl ; thus each rib, with its corresponding pair of tubercles, forms a flexuous 

 line across the outer and the under sides of the whorl : umbilicus small : the outline of the 

 septa has only been partially seen; the dorsal saddle is divided into two slightly unequal 

 parts : the specimen figured shows the beginning of a produced mouth. 



Diameter of last whorl, 1 inch ; estimated length, 4 inches. 



Only one specimen has been seen, which was found in the Chalk with siliceous grains, 

 near Lyme Eegis, by Sir H. T. de la Beche, and by him presented to the British Museum : 

 it is named in honour of his memory. 



S. Turrilites costatus, Lamarck. Plate XXVII, figs. 1 — 5, and 15, 16. 



Turbilites costatus, LamJc. 1801. An. sans Vert., p. 102. 



— Sowerby. 1813. Min. Conch., t. 36. 



— Brong. 1822. Env. de Paris, p. 83, t. 7, fig. 4. 



— Mantell. 1822. Geol. of Sussex, t. 23, fig. 15. 



— D'Orbigny. Paleont. Franc., Terr. Cret., t. 14J. 

 tkipmcatds, J. Sow. In Dixon's Geol. of Sussex, t. 29, fig. 1G. 



