FAMILY OF CARDIACEA. 



83 



LESSON VI. 



FAMILY or CARDIACEA. Cardium Donax Cyclas Corbis 



Tellina Venus Petricola Venerupis Mactra. 

 FAMILY OF INCLUSA. Lutraria My a Byssomia Hiatella 



Solen Sanguinolaria Pholas Teredo Fistulana 

 Gastrochcp.na Clamigella Aspergillum. 



CLASS OF MOLLUSCA BRACHIOPODA. General Characters 



Lingulo Terebratula Orbicula. 



CLASS OF MOLLUSCA TUNICATA, or ACEPHALA NUDA. Biphora 

 Ascidia Botryllus Pyrosoma. 



CLASS OF ACEPHALA, CONTINUED. 



1. The FAMILY OF CARDIACEA is characterized by having 

 the mantle open in front, and prolonged posteriorly into twp 

 tubes, which are sometimes ^ 



distinct, and at others united 

 in a single mass ; one of them a 

 (fiS" 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- 

 tachment of the edge of the 

 mantle, called the pallia! line (jig. 106, Z), which before 



joining the posterior muscular 

 impression or cicatrix (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 

 Fig. 106. VENERUPIS. mud. 



Fig. 105. TELLINA. 



ai 



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

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



Explanation of Fig. 106. Veneru'pis : 1. pallial line ; ai. anterior 

 muscular impression ; mi. posterior muscular impression or cicatrix. 



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

 Latin, cardium, heart.) 



