CONCHIFERA. 743 



fig. 3. The Venus islandica of BEOCCHI (and Cyprina gigas LAM.) a fossil 

 species from the calcaire grassier and other tertiary strata, does not belong 

 to this genus, but to the preceding, Venus Brocchii DESH., BKONN Leth. 

 Tab. 38, fig. i. 



Family XIV. Cycladea. Mantle concrete posteriorly, fur- 

 nished with two trachese. Ligament internal. Foot large, not 

 byssiferous. Shell equivalve, free, gibbous or ventricose. Hinge 

 with teeth under the point various, sometimes obsolete, and 

 with lateral teeth gone. Two muscular impressions remote. 



This small family contains conchifers that live in rivers and 

 in fresh-water lakes, like the Ndidea, from which it sufficiently 

 differs, although Iridina (see above, p. 736), on account of the 

 united mantle and the two trachea might be brought to it. The 

 present family is nearly allied to the preceding, whose place they 

 represent in fresh water. 



Glauconome GKAY. Cardinal teeth three, with middle one larger, 

 often bifid. Shell elongate, transverse, with points eroded. 



Fresh-water bivalves, which in external appearance almost resemble 

 Anodonta or Unio. They are all exotic. It seems that some fossil fresh- 

 water shells, which previously had been referred to the genus Venus, find 

 their true place here. 



Galathea BRUG., LAM., Potamophila Sow. Shell trigonal, sub- 

 equilateral. Teeth under the point two in right valve, with a 

 small triangular median pit receiving the third intermediate tooth 

 of left valve. Ligament prominent, turgid. Animal with two 

 traehese, not concrete, and foot oblong, compressed. 



Sp. Galathea radiata LAM. ( Venus subviridis and Venus kermaphrodila GMEL.), 

 LISTER ConcJiyl. Tab. 158, fig. 13, Encycl. metli., Vers. PI. 250, fig. i, 

 LAMARCK Ann. du Mus. v. p. 430, PI. 28, SANDER RANG Notice sur la 

 Galathee, Ann. des Sc. not. Tom. xxv. 1832, pp. 152164, PI. v. In the 

 rivers of W. Africa ; the description of RANG first made the animal known, 

 the shell alone of this species having been previously known, which some 

 writers stated to be from Ceylon. 



Cyrena LAM. Shell thick, ventricose, corticate, with points 

 eroded or decorticate. Hinge with three teeth in each valve. 

 (Animal with two tracheae separate from the base throughout.) 



Sp. Cyrena Zeylonica LAM., BLAINV. Malacol. PI. 73, fig. 2 ; a larger variety 

 of this species occurs at Java, see A. MOUSSON, Die Land- und Siteswasser- 

 Molluskenvon Java. Zurich, 1849, 8vo ; Taf - XIII A11 the species of this 

 genus are exotic. 



