TKREBRA CANALIS. 53 



Genus TEREBRA, Adanson, 1757. 

 Terebra canalis, S. V. Wood. Plate II, fig. 1. 



1848-72. Terebra canalis, S. V. Wood, Mon. Crag Moll., pt. i, p. 26, tab. iv, fig. 4, 1848 ; Mon. Crag 



Moll., 1st Suppl., p. 8, tab. iv, fig. 1, 1872. 

 1871. Terebra canalis, A. Bell, Anu. Mag. Nat. Hist. [4], vol. vii, p. 355. 

 1881. Terebra inversa, var. dextra, Nyst, Conch. Terr. Tert. Belg., p. 21, pi. ii, fig. 2 d. 

 1892. Terebra inversa, var. dextrorsa. Van den Broeck, Bull. Soc. Beige Grt'ol., vol. vi (Memoires), 



p. 131. 



Specific Characters. — Shell dextral, elongate; whorls about 10, nearly flat, 

 regularly tapering to a blunt point ; ornamented by longitudinal plications, some- 

 times numerous and inconspicuous, at other times fewer in number and strongly 

 marked, and by exceedingly fine spiral strise ; body-whorl abruptly excavated 

 below ; mouth ovate, angnlate above ; outer lip thin ; canal short, turning to the 

 left. 



Dimensions. — L. 20 mm. B. 6 — 8 mm. 



Distrihiition. — Not known living. 



Fossil: English Crag: Gedgravian ; Waltonian ; Newbournian. 

 Belgian : Poederlien. 



Remarks. — This shell, peculiar to the Pliocene deposits of the Anglo-Belgian 

 basin, has been regarded by Belgian geologists as a dextral variety of the sinistral 

 form T. inversa, but Wood considered it a different species. The two seem to have 

 been distinct in Crag times ; although nearly allied, their separation must have 

 taken place, I think, at an earlier period. The dextral shell is less common in 

 the Crag than its sinistral congener. 



Var. costata, nov. Plate II, fig. 2. 



Dimensions. — L. 20 mm. B. 7'5 mm. 



Remarks. — There are two varieties of T. canalis in the Anglo-Belgian deposits. 

 The one described by Wood, a slender and rather delicate shell with numerous 

 inconspicuous longitudinal plications, often confined to the upper whorls ; the 

 other, figured by Nyst, characteristic of the Belgian Crag, which I distinguish as 

 var. costata, being ornamented by about 15 strong and prominent flexuous costse, 

 extending nearly to the base of the shell ; this form, moreover, is more robust and 

 less elongate. Through the kindness of M. van de Wouver of Antwerp, I am able 

 to give a representation of the latter togetlier with a specimen from Oakley, which, 

 although worn, agrees with it in form and may be possibly the same ; I have 



