82 THE LAND AND FRESHWATER MOLLTJSCA OF DORSETSHIRE. 



UNIO PICTORUM, Linn., pi. 5. 



MYA OVALIS, Mont. Test. Brit., p. 34. Pult. cat., p. 27. ItacL 

 ed., p. 28, pi. 12, f. 4. 



Shell elonerated, oval, moderately thick, greenish-yellow, with 

 transverse, unequal, rugose, furrowed, brown-coloured zones ; 

 anterior end short and rounded ; posterior end produced, and slightly 

 truncate, upper margin nearly in a straight line ; ligament long and 

 straight; beaks incurved, placed about a quarter distance from the 

 anterior end ; muscular scars well denned ; pallial scars less so ; 

 inside ot shell nacrous. L.1.33. B.3. 



Hab. Ponds and rivers. River Stour (H. Seymer, and 

 Pulteney). 



Genus II.ANODONTA, Lamarck. 



The habits of Anodonta are the same as those of the Unionidas ; 

 but differ, according to Moquin Tandon in being ovoviviparous. 



1. ANODONTA CYGNEA, lAnn., pi. 5. 



MYTILUS CYGXEUS, Pult. cat., p. 38 ; Hack, ed., p. 40, pi. 12, f. 2. 

 Brit. Conch., vol. i., p. 43. 



Shell oblong, thin, transversely and irregularly grooved, some 

 times deeply so, at others the grooves are scarcely visible ; beaks 

 straight, placed about one-fourth distance from the anterior extrem- 

 ity, umbonal region compressed ; superior border almost horizontal ; 

 anterior side rounded, sloping downwards more abruptly than the 

 posterior side, which is compressed above. 0.2.75. B.5.35. 



Var. rostrata. Shell oblong oval, somewhat resembling in shape 

 Modiola vulgaris; upper margin forming a dorsal crest, which is 

 elightly raised and curved ; \anterior side rounded ; posterior side 

 attenuated, and ending in a long, curved, wedge-like point; lower 

 margin nearly straight. 



Hab. Slow rivers and ponds. Generally distributed. Var. 

 Corfe river (J. Gwyn Jeffreys). 



2. A. ANATINA, Linn., pi. 5. 

 MYTTLTTS ANATINTTS, Pult. cat., p. 38. Sack, ed., p. 40, pi. 13. f. 6. 



Shell smaller than the preceding, oval and compressed with trans- 

 verse, well defined, irregular bands, olive-green or brown, slighily 

 glossy; beaks straight, nearer the anterior end, which is rounded and 

 gaping below; posterior side forming an abruptly sloping, truncate 

 point: hinge-line straight or parallel to the lower margin ; ligament 

 short and prominent ; muscular impressions deep. L.2.1. B.3.5. 



Hab. Same as the preceeding. Generally distributed. 



