NASSA MUTABILIS. 315 



in size to an acute apex ; ornamented by exceedingly fine inconspicuous striae, 

 and near the base by fine ridges ; suture channelled, well-marked ; mouth oval, 

 angulate above; outer lip oblique, nearly straight upwards, rounded and expanded 

 below, ornamented within by fine linear ridges (not by tubercles as in N. solida) ; 

 inner lip forming a wide glaze on the pillar, ending abruptly against the deeply 

 hollowed canal ; canal very short, wide, open ; pillar sinuous, excavated in the 

 middle. 



Dimensions. — L. 25 — 32 mm. B. 14 — 20 mm. 



Distribution. — Recent : west Atlantic from Senegal and the Canaries to the 

 coasts of Spain, Portugal and south-west France. Mediterranean, widely diffused. 

 Adriatic, iEgean. Syrian coast, Egypt. 



Fossil: St. Erth (not very rare). 

 Miocene (B. D. D.). Lower Pliocene: Biot. Italy (Bellardi). 

 Pliocene : Monte Mario, Colli Astesi (abundant), Bologna. Morocco 

 (Lecointre). 



Pleistocene: Sicily — Messina, Ficarazzi, Monte Pellegrino, Catania (Nizzeti), 

 Sciacca. Calabria — Reggio, San Giovanni, Monteleone, Taranto, Gravina. Tuscany 

 — Livorno, Valle Biaia. 



Remarks. — This characteristically southern species, which has been taken as 

 the type form of Nassa, sensu stricto, has not been recorded from the Anglo-Belgian 

 basin, though it is fairly common in the western Pliocene area at St. Erth. 



It may be interesting to notice, as bearing upon the age of the latter deposit, 

 that specimens of this species from St. Erth correspond more nearly with those 

 from the Upper Pliocene of Asti, where it is very common, than with that now 

 living in the Mediterranean, which closely resembles those of the late Pleistocene 

 deposits of the sub-Etnasan beds of Nizzeti near Catania, as will be seen from the 

 figure of a recent shell here given. 



Examples of N. mutabilis from St. Erth differ from those of A. solida from the 

 same place in size and solidity, in the longer and more tumid form of the body- 

 whorl and in the internal decoration of the outer lip, which in A. mutabilis, as 

 stated above, is linear and sometimes nearly obsolete, while in N. solida it is 

 tubercular, with a strong and distinct tooth near the canal ; in the upper whorls of 

 the latter, moreover, the costation is stronger and the mouth is more oblique. 



Our St. Erth specimens of N. mutabilis approach the Buccinnm inflatum of 

 Lamarck = N. mutabilis, var. infiata of Bucquoy, Dautzenberg and Dollfus, as to 

 which the latter authors state that the internal decoration of the outer lip is some- 

 times wanting. The Sicilian form occurring at Nizzeti seems to be their variety minor. 

 Nassa mutabilis has not been reported from any horizon of the Anglo-Belgian 

 Crag, nor has it been found fossil in the western area either in the Isle of Man or 

 in the Wexford gravels. 



