168 



to have been of vegetable origin. There is, I think, very little reason 

 for doubting its being a bivalve shell ; and its general form induces me 

 to place it under this genus. I obtained it at the sale of Mr. Strange's 

 collection ; and am disposed to consider it as remarkably interesting, 

 from the singular markings which it bears. 



XCIV. Modiola. A subtransverse inequilateral bivalve ; the posterior 

 side being much the shortest, and the beaks lying towards the shorter 

 side : the hinge without a tooth, having only a marginal, linear, carti- 

 laginal groove : only one muscular impression. 



This genus is exemplified in Mytilus modiolus, Linn. The modiolae 

 are separated, by Lamarck, from the mytili, on account of their width 

 allowing them to be considered as transverse shells, of their beaks not 

 terminating the shell, and of their not attaching themselves by a bys- 

 sus, as the muscles do. He figures five species, as found in the envi- 

 rons of Paris : M. subcarinata, M. sulcata, M. pectinata, M. arcuata, and 

 M. cor data. 



Dr. Woodward describes specimens of this genus, as found in Glou- 

 cestershire, Catal. p. ii. p. 62, No. 660, &V. whence I have obtained 

 M. subcarinata. 



XCV. Anodonta. A transverse shell, having three muscular im- 

 pressions: the hinge plain, without any tooth. 



Mytilus anatinus is of this genus ; but I know of no fossil shell which 

 can be referred hither. 



XCVI. Unio. A transverse shell, having three muscular impressions : 

 an irregular callous hinge-tooth, prolonging itself on one side beneath 

 the ligamental slope, and articulating with that of the opposite valve. 



This is a river shell, which does not appear to be known fossil. 



XCVII. Nucula. An inequilateral, equivalved, subtrigonal bivalve : 

 the hinge on a line, bent at an angle formed by numerous, alternately 

 inserted teeth ; the beaks approximating, and turned backwards. 



Lamarck divides the Area of Linnaeus into three genera : Area, having 



