82 GENUS XV, ANOMIA. 



that is not pierced, which appear to serve as a stay or 



support to the animal (see Anomia Terebratida Linn., 



Cliemn. 8. t. 78. f. 707, 709). 

 Calceola. Shell with unequal valves, the largest somewhat 



like a slipper, the smaller one flat and semicircular, like 



an operculum ; the hinge with two or three little teeth 



(see Anomia Sandalium, Knorr Foss. 3. Supp. t. 206. 



f. 5 and 6). 

 HyaljEA. Shell with vmequal valves, swelled and transparent, 



gaping under the beak, and tricuspidated at the base ; 



valves united (see Anomia tridentata, Chemn. 8. vign. A 



to G. p. 65). 



Mr. Parkinson* doubts of the propriety of malung a distinct 

 genus for the Anomia Ch-yplmis, he having observed a series of 

 gradation in the curve of the beak from the more complete 

 curve of the A. Gtyphus to the slight turn of the common 

 Oyster ; but he agrees with Mr. Martin in thinking that La- 

 marck's genus of Terehratida requires a still fiirther division. 



Retzius, in the Nova Testaceonim Genera, proposed to di- 

 vide the genus Anomia into four, viz. Anomia, Crania, Tere- 

 bratula, and Placenta (see Linn. Trans, vol. 7. p. 205). 



Perhaps we may place here Lamarck's genus Trigonia, and 

 Mr. Parkinson's Harpax, which are described as follow : 

 Trigonia. Shell inequilateral, nearly triangular ; the hinge 



* Organic Remains, vol. 3. p. 21(t 



