FAMILY 4. MYARIA. 53 



THRACIA, Leach. 



Testa ovalis, oblonga, subaequilateralis, inaequivalvis, utroque latere pau- 

 luliim hians. Cardo dente in utraque valva plus minusve prominulo, 

 horizontali, cochleariformi , ligamentum excipiente. Impressio mus- 

 cularis pallii profunde imbuta. 



By adopting the genus Thracia of Dr. Leach, we are enabled to asso- 

 ciate a very natural and distinct group of Myaria, that Lamarck had 

 included with his Anathue. 



Their shell is oval, oblong, and inequivalve ; it is also thin, fragile, and 

 gaping at both sides, The hinge consists of a more or less prominent, 

 horizontal, spoon-shaped tooth in each valve, receiving the ligament ; 

 and the palleal impression is deeply marked. 



Examples. 



PI. XXXV. Fig. 1. 



ThraciX phaseolina, Kiener, Iconographie des Coquilles vivantes, pi. 2. 



f. 4. 

 Amphidesma phaseolina, Lamarck. 



PL XXXV. Fig. 2. 



Thracia plicata, Deshayes, Enc. Meth., vol. iii. p. 1039. Kiener, Ico- 

 nographie des Coquilles vivantes, pi. 2. f. 3. 



PI. XXXV. Fig. 3. 



Thracia corpuloides, Deshayes, Diet. Classe d'Hist. Nat., vol. xvi. f. 4. 

 De Blainville, Manuel de Malacologie, pi. 76. f. 7. 



