Elements of conchology Prepared Elements of conchology / Prepared for the use of schools and colleges elementsofconcho00rusc Year: 1844 Fig. 101.—UNio. We also place in this same group certain marine mollusks, which resemble the Unios in their organization and the general disposition of the hinge, but in which the beaks (summits) of the shell are more arched, and from which projecting ribs radiate towards the circumference; such are the genus Car- DiTA, the form of which is more or less oblong or cordiforrn (heart-shape); the Cypricardia, in which the tooth beneath the summit oftheshell is d
Elements of conchology Prepared Elements of conchology / Prepared for the use of schools and colleges elementsofconcho00rusc Year: 1844 Fig. 101.—UNio. We also place in this same group certain marine mollusks, which resemble the Unios in their organization and the general disposition of the hinge, but in which the beaks (summits) of the shell are more arched, and from which projecting ribs radiate towards the circumference; such are the genus Car- DiTA, the form of which is more or less oblong or cordiforrn (heart-shape); the Cypricardia, in which the tooth beneath the summit oftheshell is divided into two or three; theCoRALLioPHAGA, in which the shell is thin and the lateral plate much effaced, &c. 26. In the Family of Chamacea the mantle is closed and perforated by three open- ings only; through the anterior one passes the foot {fg. 102, p) ; the next (r) gives passage to the water necessary for res- piration, and the third (e) is for the expulsion of effete matters. As we have already stated, the last two openings are not prolonged into tubes, as in the next two families. And the hinge is very analo- y. g gous to that of the Unios ; for the left valve has a tooth near ^'^-IOS—chama, without its shell. the summit, and further back, a projecting plate, which are re- ceived into fossse (pits) in the opposite valve. Explanation of Fig. 102.—A Chama divested of its shell to show the dis- position of its mantle :—p. the foot;—r. opening for respiration ;—e. the opening for the passage of excrement. 26. What are the characters of the family of Chama'cea ?
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