138 CLASS I. TROPIOPODA. ORDER II. UNIMUSCULOSA. 



we can feel tbe propriety of retaining a genus where we would not venture 

 to create one ; our object being to follow both the established nomencla- 

 ture, and the popular form of classification, as long as they accord with 

 the progress of discovery. 



The shell of Modiola may be described as being oblong, equivalve, 

 regular and inequilateral, with the anterior side very short, obtuse, and 

 a little gaping. The hinge is linear, consisting of a long, almost internal 

 marginal ligament. The muscular impression is compound and sub- 

 lateral. 



Examples. 



PI. C. Fig. 1 . 



Modiola picta, Lamarck, Anim. sans vert., vol. vii. p. 21. Enc. Meth., 



pi. 221. f.2. 

 Mytilus arborescens, Chemnitz. 

 Mytilus pictus, Deshayes. 



PL C. Fig. 2. 



Modiola silicula, Lamarck, Anim. sans vert., vol. vii. p. 25. Sowerby, 



Genera of Shells, No. 26. 

 Mytilus siliculus (De Blainville ?). 

 Mytilus cinnamomeus, var., Deshayes. 



PI. C. Fig. 3. 

 Modiola discrepans, Lamarck, Anim. sans vert., vol. vii. p. 23. Pay- 



randeau, Cat. Moll, de Corse, p. 67. Sowerby, Genera of Shells, 



No. 26. 

 Mytilus discors, Deshayes. Linnaeus ? 



PI. C. Fig. 4. 

 Modiola discors, Lamarck, Anim. sans vert., vol. vii. p. 23. Enc. Meth., 



pi. 204. f. 5. a, b. Sowerby, Genera of Shells, No. 26. 

 Mytilus discors, var., Gmelin. 

 Mytilus cor, Martyn. 

 Mytilus impactus, Dillwyn. 



