78 SAXICAVID.E. 



the Jurassic epoch; Searles Wood, however, believes 

 that it was not born before the tertiary formation. 



1. Saxicava Norve'gica*, Spengler. 



My a norvegica, Spengl. Skrivt. Nat. Selsk. iii. (1). p. 46, t. ii. f. 18. 

 Panopcsa Norvegica, F. & H. i. p. 174, and app. iv. p. 249, pi. xi. and 

 (animal) pi. W. f. 1. 



Body oblong, pale pinkish drab : mantle covered with a black 

 skin : tubes protected by a dark-brown leathery sbeath, some- 

 what unequal in length, the upper or excretal tube being the 

 shorter and smaller of the two ; orifice of the larger tube 

 encircled by 30-40 short tentacular cirri, of a brick-red 

 colour, alternately large and small, and sometimes folded back 

 on the edges of that tube ; the smaller tube is also fringed, but 

 much less distinctly : gills irregularly pectinated : palps long, 

 delicate, slender and pointed, united around the mouth : foot 

 very small when contracted : liver green. 



Shell oval with a somewhat oblique and irregular outline, 

 the right valve a trifle larger than the left, moderately convex; 

 it has a broad furrow in the middle gradually enlarging towards 

 the front, a considerable gape between that part and the 

 anterior side, and a remarkably large and wide opening at the 

 posterior end ; it is thick, opaque, and lustreless : sculpture, 

 coarse, distant, and irregular concentric wrinkles: colour whitish, 

 occasionally stained with a ferruginous tinge : epidermis pale 

 yellowish -white, puckered in every direction, not continued 

 over the tubular sheath, which is of a fibrous nature : margins 

 rounded or obtusely angular on the anterior side, nearly straight 

 or slightly incurved in front, obliquely truncated on the pos- 

 terior side, and a little reflected outwards in adult examples ; 

 dorsal edges sloping gradually on each side, the posterior one 

 being usually more than twice the length of the other : beaks 

 blunt and much inflected: ligament large, horncolour : hinge- 

 line almost straight : hinge-plate broad and thick, excavated 

 for the reception of the teeth, and furnished with a short but 

 solid process for the ligament, which is reflected outwards and 

 callous in younger shells : teeth, in the right valve a compara- 

 tively minute cardinal, and in the left valve two others of even 

 a smaller size, which are placed so near together as scarcely 

 to allow space for receiving between them the opposite tooth : 



* Norwegian. 



