FAMILY OF CARDIACEA. 



LESSON VI. 



FAMILY OF CARDIACEA. Cardium Donax Cyclas Corbis 



Tellina Venus Petricola Venerupis Mactra. 

 FAMILY OF INCLUSA. Lutraria My a. Byssomia Hiatella 



Solen Sanguinolaria Pholas Teredo Fistulana 

 Gastrochana Clavagella Aspergillum. 



CLASS OF MOLLUSCA BRACHIOPODA. General Characters-^- 



Lingulo Terebratula Orbicvla. 



CLASS OF MOLLUSCA TUNICATA, or ACEPHALA NUDA. Biphora 

 ^4 scidia Botryllus Pyrosoma. 



CLASS OF ACEPHALA, CONTINUED. 



1. The FAMILY OF CARDIACEA is characterized by having 

 the mantle open in front, and prolonged posteriorly into two 

 tubes, which are sometimes 



distinct, and at others united 

 in a single mass ; one of them a 

 (jig- 105, r) serves for respi- 

 ration, and the other (e) for 

 the passage of excrement. 

 This mode of conformation is p 

 recognised in the shell by the 

 impression made by the at- 

 iachment of the edge of the 

 mantle, called the pallial line (fig. 106, Z), which before 



joining the posterior muscular 

 impression or cicalrix (mi), 

 curves more or less deeply in- 

 I wards. In all these mollusks, 

 there is a transverse muscle 

 and a foot (fig. 105, p), which 

 generally enables the animal to 

 crawl. The species of Cardia- 

 cese that have long tubes, ordi- 

 narily live buried in the sand or 

 mud. 



Fig. 105. TELLINA. 



mi 



ai 



Fig. 106. VENERUPIS. 



Explanation of Fig. 105. Tellina : a. the shell ; 6. the hinge ; r. tube 

 for respiration ; e. tube for excrement ; p. the foot. 



Explanation of Fig. 106. Veneru'pis : /. pallial line; at. anterior 

 muscular impression ; mi. posterior muscular impression or cicatrix. 



1. How is the family of Cardia'cea characterized ? (Cardiacea, from the 

 Latin, cardium, heart.) 



