316 PLIOCENE MOLLUSCA. 



Var. erthensis, S. V. Wood, MS. Plate XXXIII, fig. 26. 



1886. Nassa mutabilis, var. St. Erthensis, S. V. Wood, MS., in Kendall and R. G. Bell, Quart. Journ. 



Geol. Soc, vol. xlii, p. 210. 

 1898. Nassa mutabilis, var. St. Erthensis, A. Bell, Trans. Roy. Geol. Soc. Cornwall, vol. xii, p. 140, 



pi. i, fig. 5. 



Varietal Characters. — Much larger and longer than the type, the outer lip 

 being more expanded, and the upper part of the whorls obtusely and obscurely 

 angulate rather than rounded; in R. G. Bell's MS. sub-variety gigantea (loc. cit.) 

 the whole of the shell is said to be spirally striated. 



Dimensions.— L. 45 — 54 mm. B. 25 — 32 mm. 



Distribution. — Not known living. 

 Fossil : St, Erth. 



He in tries. — The principal difference between this form and the type is its much 

 larger size, one of the specimens here represented attaining a length of 54 mm. 

 Generally they are smaller, about 45 mm. Prof. Sacco figures a large variety of 

 N. mutabilis, apparently thick and coarse-looking, with strong sculpture, under 

 the name of var. pliomagna (op. cit., pt. xxx, pi. xv, figs. 27, 28), but it does not 

 altogether agree with the present shell. 



No recent variety of N. mutabilis is known which, approaches in size the present 

 form. Taken as a whole the St. Erth Nassas are strikingly different from those 

 of the English Crag, the common Red. Crag species of that genus being almost 

 without exception conspicuous by their absence. Mr. R. B. Newton regards the 

 St. Erth fauna as older than that of the Coralline Crag. 1 



N. Carditis, Brongniart, a Miocene species, has a superficial resemblance to 

 N. mutabilis and especially to the present variety, but it is now generally regarded 

 as belonging to a different genus. 2 



Nassa Kennardi, F. W. Harmer. Plate XXXV, figs. 4, 5. 



1897. Buccinum (Cominella) aquitanicum, A. Bell, Trans. Roy. Geol. Soc. Cornwall, vol. xii, p. 139. 

 1914. Nassa Kennardi, F. W. Harmer, Plioc. Moll. Gt, Brit., pt. i, p. 87, pi. v, fig. 11. 



Distribution. — Fossil: St. Erth. Scaldisien : Antwerp (additional). 



Remarks. — One of the fossils here represented is from the Scaldisien of Antwerp, 

 the other from the St. Erth collection at the British Museum, the latter having 

 been identified with a Miocene shell, Buccinum aquitanicum (Mayer), from south- 

 west France. 3 Comparing it, however, with a typical specimen of that form 



1 Journ. of Conch., vol. xv, p. 137, 1916. 



- See figures in Homes, op. cit., pi. xii, figs. 1 — 3. 



s Journ. de Conch., vol. vii, p. 192, pi. iv, fig. 2, 1858. 



