254 aporrhaid^e. 



fold long and narrow: operculum slighter than that of A.pes- 

 pelecani, but agreeing with it in other respects. L. 1*2. B. (to 

 the furthest spike of the pterygoid flap) 1. 



Habitat : Muddy sand in 40-85 f. on the east coast 

 of Shetland, at a distance from land of 6-50 miles 

 (M f Andrew, Barlee, and J. G. J.) • it is gregarious, 

 although very local. M*" Andrew and Barrett dredged a 

 single dead specimen off the coast of Upper Norway, at 

 a depth of 70 f. • but no Scandinavian zoologist appears 

 to have met with it. 



This mollusk is not so inactive as its associate, A. pes- 

 pelecani. Its faeces are oval and brownish. Mon- 

 strosities'of the shell sometimes occur : one has the top 

 spike double or forked, another has four digitated pro- 

 cesses on the outer lip, and in a third the top spike is 

 attached to the lower five whorls. Some specimens are 

 much smaller than others; I have given the average 

 dimensions. 



A. pes-carbonis of Brongniart (a fossil of the upper 

 Miocene formation of Bordeaux and Antwerp) is equally 

 small, but a much stronger shell; and the basal process 

 is short, spear-head-shaped and incurved, as in A. pes- 

 pelecani. The present species differs from A. Serresiana 

 (a Mediterranean shell) in its smaller size, delicate tex- 

 ture, fewer and rounded (instead of angulated) whorls, 

 and in the spire being much less tapering. Size alone 

 is, of course, not an infallible criterion of distinctness — 

 especially if we take into account the depth of water and 

 distance from land ; but it is remarkable that Zetlandie 

 specimens of Pecten aratus (P. Bruei) , P. Testce, P. 

 septemradiatus, var. Dumasii, Tellina balaustina, and 

 many other species are larger than those from the south 

 of Europe. If Philippi had not described his Chenopus 

 desciscens (a Palermitan and Calabrian fossil) as having 



