92 MOLLUSCA. 



To Lamark we are also indebted for having formed the 

 genus CALCEOLA from the anomia sandalum of Linnaeus. 

 The largest valve is sandal-shaped, and has at the hinge two 

 or three small teeth. The other valve is small, flat, semi- 

 orbicular, and resembles an operculum. It is frequent in a 

 fossil state in Germany. 



Mr. Sowerby, in his valuable work on British Mineral 

 Conchology, has made us acquainted with several new 

 genera of fossil shells, which, by the older naturalists, would 

 have been inserted in the genus Anomia. The genus PEN- 

 TAMERUS is an equal-sided inequivalve bivalve, with one 

 valve, divided by a longitudinal internal septum into two 

 parts, the other by two septa into three parts or valves. Beaks 

 incurved, imperforate. He has figured three species of this 

 curious genus. 



The genus PLAGIOSTOMA of Sowerby, is represented by 

 the Pectenites Plagiostomus of Luid, (tab. 10, f. 639,) and 

 is thus defined : " An oblique eared bivalve, hinge destitute 

 of teeth or internal pit. Line of the hinge straight in one 

 valve, in the other deeply cut by an angular sinus." He 

 gives figures of two species in his first volume, the gigan- 

 tea and the spinosa ; and many others have been subse- 

 quently detected. 



The genus DIANCHORA is nearly related to the preced- 

 ing, but in this the shell is fixed, and the attached valve has 

 an opening in place of a beak. The other valve is beaked 

 and eared. 



The anomia spinosa of Linnaeus probably belongs to Mr. 

 Sowerby's genus PRODUCTUS, which he thus defines : " An 

 equilateral unequal-valved bivalve, with a reflexed, more or 

 less cylindrical margin ; hinge transverse, linear ; beak im- 

 perforate ; one valve convex, the other flat or concave ex- 



