7Q PLIOCENE MOLLUSCA. 



1881. Nassa elegans, Nyst, Couch. Terr. Tert. Belg., p. 29, pi. ii, &». 11. 

 1885. Nassa elegans, Lorie, Arch. Mus. Teyler [2], vol. ii, p. 90, pi. v, fig. 18. 

 1912. Nassa consociata, Tescli, Med. v. d. Eijks. v. Delfstoffen, pt. iv, p. 80. 



Specific Characters. — See Mon. Crag Moll., pt. i, fig. 31. 



Dimensions. — L. 15 — 20 mm. B. 8 — 10 mm. 



Distribution. — Not known living. 



Fossil : Coralline Crag : Gedgrave, Sntton, Boyton. Waltonian : 

 Walton-on-Naze, Beaumont, Little Oakley. Newbournian : Waklringfield, Foxhall, 

 Newbourn, Sntton, Felixstow. Butleyan : Bntley. Isle of Man. Scaldisien : 

 Belgium, Holland. 



liemarJiS. — We have two varieties of JSf. consociata in the Crag, a short form, var. 

 hrevis, about 15 mm. in length, and another, with an elongate spire, which occa- 

 sionally reaches 20 mm. I have found both in fair abundance at Oakley (about 

 50 of each). 



This species made its first appearance in the Anglo-Belgian basin at the 

 G-edgravian stage, becoming gradually less abundant in the later beds of the 

 Eed Crag, and being unknown from any deposits newer than those of Butle}'. It 

 is allied to N. elegans, but has always been regarded as distinct, differing from 

 the latter both in form and sculpture. N. consociata is a more slender shell, with 

 an elongate and quasi-cylindrical spire ; the cost^e, both longitudinal and trans- 

 verse, are stronger and more clearly granulate at the points of intersection. In 

 N. elegans the suture is deeper and the whorls more decidedly convex, the last 

 being wider in proportion to the length of the spire ; the longitudinal ribs are 

 almost knife-edged, instead of strong and rounded, as in N. consociata. It appears 

 that Nyst reversed the names of these two species. The s^oecimen figured b}^ him 

 in 1S43 as N. elegans [op. cit., pi. xliii, fig. 13), Avhich is the more common form 

 of the Scaldisien deposits and is still known in Belgium under that name, should 

 be referred, I think, to Wood's species N. consociata. It differs slightly from the 

 Crag shell, but is still further removed from Sowerb^^'s N. elegans. I have given 

 it in the present work (PI. IV, fig. 18) as N. consociata var. belgica. Dr. Lorie's 

 figure {op. cit.) seems to represent a short form of the same variety. 



During a recent visit to the Isle of Man Mr. A. Bell discovered a specimen of 

 the variety hrevis near Cranstal point. 



In the paper quoted above Jeffreys states, but I Ijelieve in error, that both the 

 present species and N. elegans are living in the Atlantic and West European seas.^ 



Nassa elegans (Leathes, MS.) (J. Sowerby). Plate IV, figs. 19, 20. 



1825. Buccinum elegans, J. Sowerby, Miu. Couch., vol. v, p. 121, tab. cccclxxvii, fig. 1. 

 1848. Nassa elegans, S. V. Wood, Mou. Crag. Moll., pt. i, p. 30, tab. iii, fig. 1. 

 1881. Nassa consociata, Nyst, Couch. Terr. Tert. Belg., p. 24, pi. ii, fig. 5. 



1 M. Dollfus writes me that neither species is kuowu to him living, either in the regions named 

 or elsewhere. 



