Unionidae sentence example
- The chief points in which they vary are - (1) in the structure of the ctenidia or branchial plates; (2) in the presence of one or of two chief muscles, the fibres of which run across the animal's body from one valve of the shell to the other (adductors); (3) in the greater or less elaboration of the posterior portion of the mantle-skirt so as to form a pair of tubes, by one of which water is introduced into the sub-pallial chamber, whilst by the other it is expelled; (4) in the perfect or deficient symmetry of the two valves of the shell and the connected soft parts, as compared with one another; (5) in the development of the foot as a disk-like crawling organ (Arca, Nucula, Pectunculus, Trigonia, Lepton, Galeomma), as a simple plough-like or tongueshaped organ (Unionidae, &c.), as a re-curved saltatory organ (Cardium, &c.), as a long burrowing cylinder (Solenidae, &c.), or its partial (Mytilacea) or even complete abortion (Ostraeacea).
- In Unionidae and several other forms the pericardial glands are extended into diverti cula of the pericardium which penetrate the mantle and constitute the organ of Heber.
- Mutelidae.-Differs from Unionidae in having two pallial sutures; freshwater.
- The family Unionidae, to which these genera belong, is of world-wide distribution, and its species occur only in ponds and rivers.
- Over 40 species of freshwater mussels (Unionidae) have been observed in the Rumanian rivers.Advertisement