PHOLADIDEA. 117 



lar plate in each valve (somewhat longer in the right), which 

 interlock and seem analogous to cardinal teeth in other bivalves : 

 apophyses curved, frequently twisted, narrow, and rather short : 

 dorsal shields often united, so as to form a single plate only, 

 which in that state is not unlike the shield in Pholas crispata ; 

 it is also deeply scored by the lines of growth : inside porcel- 

 lanous and glossy, showing on the anterior side the impres- 

 sions of the outside sculpture, and marked with a strong ridge, 

 which corresponds to the outside groove and terminates in a 

 blunt tubercle: sca^^s as in Pholas crispata: the call/ ci form 

 appendage is capacious, expanding considerably outwards, with 

 the edges slightly reflected ; it is divisible into two parts, one 

 belonging to each valve. L. 0-75. B. 1-5. 



Var. ahorta. Shell stunted and sometimes distorted, vary- 

 ing in size from 4-th to Jths of an inch, exclusive of the 

 terminal process. 



Habitat : New red sandstone or trias, at low-water 

 mark on the South Devon coast (Turton and others) ; 

 Hayle (Miss Hockin) ; peat_, at BaUycotton^ co. Cork 

 (Wright) ; submarine forest^ Clonea near Dungarvan 

 (Farran) ; Dublin Bay ? (Thompson) ; sandstone at low 

 water^ Castle Chichester near Belfast (Hyndman). The 

 variety has been taken from lumps of hard clay dredged 

 in deep water off Exmouth (Clark) ; in a piece of reddish 

 sandstone from deep water on the Cornish coast^ drawn 

 up by a fisherman^ s line (Couch) ; in soft sandstone 

 dredged in 80 f. off the coast of Antrim (J. G-. J.) ; in 

 indurated clay from 25 f. near Lismore in the west of 

 Scotland^ with Nucula sulcata (Bedford) . Mr. Searles 

 Wood detected some shelly fragments which he referred 

 to P. papyracea in the Coralline Crag at Sutton ; other- 

 wise it appears to be unknown as a fossil. No foreign 

 locality has been recorded. 



The burrows are occasionally flexuous. One of these 

 in sandstone has near its opening a piece of silex much 

 larger than the rest^ which the animal appears to have 



