Elements of conchology Prepared Elements of conchology / Prepared for the use of schools and colleges elementsofconcho00rusc Year: 1844 8. The Venus '^^^.^.tl'''^''''^ { Ji -I A-y\ • • /LIGAMENT-. \ {fig' 107) IS re- cognised by the hinge, the ante- ^'\ rior and poste- rior plates of ^ ' which, instead of being- sepa- rated from the middle tooth, as -^ in the Cardia, &c., are approxi- mated in a sin- gle group be- neath the sum- mit. The shell Fig. 107.—venus. is generally thick, moderately convex, and a little elongated The species of this genus are very numerous. 9. The genera Petricola an
Elements of conchology Prepared Elements of conchology / Prepared for the use of schools and colleges elementsofconcho00rusc Year: 1844 8. The Venus '^^^.^.tl'''^''''^ { Ji -I A-y\ • • /LIGAMENT-. \ {fig' 107) IS re- cognised by the hinge, the ante- ^'\ rior and poste- rior plates of ^ ' which, instead of being- sepa- rated from the middle tooth, as -^ in the Cardia, &c., are approxi- mated in a sin- gle group be- neath the sum- mit. The shell Fig. 107.—venus. is generally thick, moderately convex, and a little elongated The species of this genus are very numerous. 9. The genera Petricola and Venerupis (j%%%%%%%%%%%%%%%%. 106) resemble the Venus very much, and have obtained their names from living in the interior of stones which they perforate. 10. The Mactr^ differ from other cardiaceas in having an internal ligament, lodged in two pits in the hinge, corresponding v/ith each other i^jig. 108). There are some large species on our own coast. 11. The fifth and last family of testaceous acephalse or Inclusa, is composed of mollusks in which the mantle is only open at its an- terior extremity, or near the mid- dle, for the passage of the foot, and is prolonged posteriorly in a double tube ; in other parts it is completely closed {fig- 109). The shell is always gaping at the Explanation of Fig. 107.—Cytherea, or Venus ;—s. the summit or beak ;— I. the lunula ;—p. pit;—A. anterior, and P. posterior extremity of the shell. 8. What are the characters of the genus Venus ? 9. From what circumstance do the genera Petrico'la and Venerupis ob- tain their names? (Petricola, from the Latin, petra, a stone, and colo^ I inhabit.—Venerupis, Latin, Venup,and rupes, a rock.) 10. How is the genus Mac'tra characterized ? (Mactra, Latin, a trough.) 11. What are the general characters of the family of Inclusa? (Inclusa^ Latin, enclosed.) Fig. 108. MACTRA. 8
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