WORMS. W 



38. t'ELLINA. Inhabitant a Tethys : shell generally slop- 

 ing and somewhat curved on one side : hinge with, 

 generally 3 teeth* the lateral-ones in one valve flat or 

 nearly obsolete. 



39. CARDitJM. Inhabitant a Tethys ; shell of equal con* 

 vex valves* ribbed or striate longitudinally* toothed 

 round the edges t hinge with 2 teeth near the beak* 

 and a larger remote one on each side* each locking 

 into the opposite valve. 



40» M act ft A. Inhabitant a 'tethys : shell with equal 

 valves* unequal at the sides: hinge with thfe middle 

 tooth complicated* with a small hollow each side; 

 the lateraMeeth remote and locking into the oppo- 

 site valve. 



41. Donax. Inhabitant a Tethys : shell with the ante* 

 rior margin very obtu se and generally crenulate : hinge 

 with 2 teeth in the middle* and a single remote late« 

 ral one. 



42. Venus; Inhabitant a Tethys : shell with the attteri* 

 or margin of the lip of one valve generally incumbent 

 on the other : hinge with 3 teeth* all close together, 

 the lateral-ones diverging from their tips. 



43. Cham A. Inhabitant a Tethys : shell strong* rather 

 coarse; hinge rugged* gibbous* the teeth Obliquely 

 locking into the opposite valve. 



44. Arc A. Inhabitant a Tethys: shell of equal valves 1 

 hinge with numerous sharp teeth alternately locking 

 between eacli other. 



45. Pecten. Inhabitant a Tethys: shell of unequal 

 valves* mostly ribbed or striate longitudinally* with 

 an ear-like process oil one or both sides the hinge : 

 hinge without teeth* but furnished with a small some- 

 what triangular hollow. 



46. Ostrea. Inhabitant a tethys: shell of Unequal 

 rugged or plaited valves without the ear-like pro- 

 cess : hinge without teeth, with a transverse striate 

 cavity. 



47. AnomiA. Inhabitant hdt reducible to any genus of 

 Mollusca: shell of unequal valves* one of then! 

 flattish and mostly perforated near the base, the 

 other Convex at the base with a produced beak : 

 hinge a transverse linear prominence on the flat valve 

 Connected by a strong Oartilage under the beak of the 

 opposite valve. 



48. MYTiLts. Inhabitant allied to an Ascidia : shell 

 generally affixed by a beard of silky filaments : hinge 

 without teeth, marked by a longitudinal groove 

 which is sometimes crenulate. 



49. Pinna. Inhabitant allied to an Ascidia: shell fra 



