CALCEOLA. 



upper edge arched. It is in this large valve, that the 

 fibrous or rather interruptedly porous structure, which 

 has given rise to the opinion of its belonging to the Poly- 

 paria, is generally observable. The upper or smaller valve 

 is flattish, semiorbicular ; it has the appearance of an 

 operculum to the large hollow valve, and is semicir- 

 cularly striated; its internal cardinal edge is furnished 

 according to Lamarck, for we have never seen it, with 

 two lateral tubercles, a central pit, and a small plate. 



The Calceola is distinguished from all other bivalves, 

 by its form, something like a ladies slipper, without a 

 heel, by its thickness and solidity, by its being striated 

 internally from the center to the circumference, and by 

 having no ligament. It is a fossil; found, as we are 

 informed, in the environs of Juliers ; and, as we suppose, 

 in the Mountain Limestone : its nearest analogues are 

 some Mountain Limestone fossils, represented in " Mar- 

 tin's Petrif. Derbiens, under the name of Anomta cuspidata; 

 and in Sowerby's Mineral Conchology, under that of 

 Spirifer cuspidatus; which, however, can hardly be con- 

 founded with it, as its characters are sufficiently distinct. 



The Calceola is supposed to have been marine : only 

 one species is known, the Calceola */uliacensis*, of this we 

 have given three view&in our plate. 



* Anomia Sandalinm, Linn.; Calceola sandalina, Lam.j in our plate it is 

 called C. Sandalium, but wc prefer the above name. 



