870 PELE< YPODA. [Filibrnnchiri. 



Diameter Ant. -post.. 42mm.; dorso-ventral, 27mm.: thick- 

 ness, 25 mm. 



Hob. North and South Islands of New Zealand. Chatham Islands. 

 Also Australia. Brought to England by Captain Cook. From low- 

 water mark to about 25 fathoms, between boulders and rocks ; usually 

 a number of shells in a nest of byssus threads. 



Fossil in the Pliocene. 



Genus 4. LITHOPHAGA, Bolten, 1798. 



Lithophaga, Bolten, Mus. Bolten. (2). 1798, 156. Type : Mytilu* litln- 

 phagus, L. Lithophagus, Megerle, Entwurf, 1811, 69. Liihodomus, 

 Cuvier, Regne An., ii, 1817, 471. Leiosolenus, Carpenter, Mazatlan Cat., 

 1856, 130. Myoforceps, Fischer, Man. Conch., 1886. 969. 



Animal as in Mytilus ; the foot short, byssiferous. 



Shell equivalve, transverse, oblong, subcylindrical, rounded in 

 front, with an epidermis, very inequilateral. Beaks anterior, not 

 much produced ; anterior end rounded, posterior end rostrate or 

 cuneiform ; hinge-plate linear, without teeth ; ligament marginal, 

 internal ; interior with a thin nacreous layer ; outer layer of shell of 

 tubular structure. 



Distribution. About twenty-five species from the Gulf of Gascogne. 

 Mediterranean, Antilles, Indian Ocean, Pacific, New Zealand. 



Fossil in the Secondary and Tertiary. 



Remarks. The young shells are fixed by their byssus, but later on 

 they begin to bore into shells and rocks, the excavation being of the 

 same shape as the shell, and allowing no rotatory movement. The 

 animal is phosphorescent. 



One species. L. stn'ata. Hutton. is recorded from the Pliocene of 

 Wanganui. 



1. Lithophaga truncata, Gray. 1843. Plate 5r\ fig. 8. 



Lithodomus trunnitux, (Jray. Diet?. X.Z.. 2r>9 ; C.M.M., 79 ; |Crit. List. 4s ; 

 Conch. Icon., x, f. 3 : Ereb. & Ter.. 6, pi. 2. f. 12 : M.N.Z.M.. His. Lltho- 

 i. ( irav. Index, 94. 



Shell oblong, subcylindrical, equivalve, inequilateral, thin, dark 

 brown, shining. Beaks prominent, near the anterior end, close together, 

 swollen and innexed. Anterior end short, ventricose, convex, the dorsal 

 margin first lightly convex, then straight ; from the inner side of the 

 umbones a low ridge runs down to the posterior end of the basal margin. 

 Posterior end produced and tapering, narrowly rounded ; basal margin 

 concave on its anterior half, slightly convex behind. Anterior area 

 short, slightly excavated under the beaks : posterior area narrowly 

 and elongately lanceolate, deep behind the beaks. Sculpture con- 

 sisting of concentric strise and ridges, and a few radiate lines below 

 the umbones. Kjiiilerniift brown, thick and persistent, polished. 



