XYLOPHAGA. 89 



Exmouth, and others in Mr. Hanley's cabinet, which he 

 procured from ship-timber at Bristol. Strictly speaking 

 then, this ought not to be included in our Fauna, as we 

 have no evidence of its propagation in this country. The 

 terminal portion of the tube was concamerated In the wood 

 which accompanied Mr. 01ark''s examples ; we confess, 

 however, we perceived no indication of such structure in 

 the very small perforations of the Irish specimens ; in both 

 the testaceous matter was sparingly deposited. 



XYLOPHAGA, Turton. 



Shell globular, closed posteriorly, much and angularly 

 open anteriorly, composed of two equal, much-curved, 

 anteriorly emarglnate valves, their outer surfaces divided 

 into various ornamented and smooth portions, the inner 

 strengthened by a strong longitudinal rib or apophysis 

 running from beak to ventral margin ; muscular impres- 

 sions two, posterior large, round, anterior small, sub- 

 marginal. A single distinct and curved denticle beneath, 

 but not under, the beak. Back of the shell anteriorly 

 furnished with two (complicated) accessory valves. No tube. 



The animal of our British species, according to a note 

 kindly communicated by the Rev. David Landsborough, is, 

 with the exception of the siphons, entirely included within 

 the shell. The foot is large, and pillar-shaped ; its ex- 

 tremity tinged with buff. It occupies the greater part of 

 the anterior opening, and may be protruded to some length. 

 The margin of the mantle around it appears to be plicated. 

 The rest of the animal is white. The siphons are very ex- 

 tensible ; sometimes assuming a length of three-quarters of 

 an Inch, more usually resting at about the third of those 

 dimensions. Such an animal has evidently much closer 



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