390 



MAISTJAL OF THE MOL-LUSCA, 



SlPHONOTRETA, Yerneuil. 



JEtymoJogy , sipJion, a tube, tretos, perforated. 



Types, S. unguiculata, Eicli-w., Figs. 199, 201. S. verrucosa, 

 Pig. 200. 



SheU oval, bi-convex, slightly beaked, conspicuously punctate, 

 or spiny ; beak perforated by a tubular foramen ; hinge-margins 



fig. 199. 



Fig. 200. Exterior. 



Fig. 201. Interior. 



thickened ; ventral valve with four close adductor scars sur- 

 rounding the foramen. The spines are tubular, and open into 

 the interior of the shell by prominent orifices. (Carpenter.) 

 S. anglica, Morris, has moniliform spines. 



Fossil, 9 species. Lower and Upper Silurian. Britain, 

 Bohemia, Russia. 



? Acrotreta (sub-conica), Kutorga. 3 species. Lower Silurian, 

 Russia. Shaped like Cyrtia, with an apical foramen ; no 



hinge. 



Family VIII. — Lustgulid^^. 



Shell oblong or orbicular, sub -equi valve, attached by a pedicle 

 passing out between the valves ; texture horny, minutely 

 tubular. 



Animal fwith a highly vascular mantle, fringed with horny 

 setse ; oral arms thick, fleshy, spiral, the spires directed inwards, 

 towards each other. 



LnsTGULA, Bruguiere. 



Etymology, lingula, a little tongue. 



Type, L. anatina, PI. XY., Fig. 32. 



Shell oblong, compressed, slightly gaping at each end, trun- 

 cated in front, rather pointed at the umbones ; dorsal valve 

 rather shorter, witlji a thickened hinge-margin, and a raised 

 ceiitral ridge inside. 



