FAMILY OF CARDIACEA. 



83 



LESSON VI. 



Family of Cardiacea. — Cardium — Donax — Cyclas — Corbis 



— Tellina — Venus — Petricola — Venerupis — Mactra. 

 Family of Inclusa. — Lutraria — Mya — Byssomia — Hiatella 



— Solen — Sanguinolaria — Pholas — Teredo — Fistulana—' 

 Gastrochmna — Clavagella — Aspergillum. 



Class of Mollusca Brachiopoda. — General Characters-— 



Lingulo — Terebratula — Orbicula. 

 Class of Mollusca Tunicata, or Acephala Nuda. — Biphora 

 — Ascidia — Botryllus — Pyrosoma, 



CI.ASS OF ACEPKAIiA, 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- 

 tachment of the edge of the 

 mantle, called the pallial line {fg. 106, Z), which before 



joining the posterior muscular 

 • impression or cicatrix (m), 

 curves more or less deeply in- 

 l wards. In all these mollusks, 

 there is a transverse muscle 

 and a foot {fg. 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 

 Fis. 106.— vENERUPis. mud. 



Fig. 105. — TELLINA. 



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 : — I. 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.) 



