438 



MONOGRAPH OP THE GENUS 



PEDUM. 



Class, Conchifera. Order, Monomyaria. Fam., Pectinides. 



Gen. Char. " Testa insequivalvis, subauriculata ; valva inferiori 

 hiante ; natibus insequalibus, divaricatis. Cardo edentulus. Liga- 

 mentum partim externum, in fossula canaliformi natium pariete 

 interna affixum. Valva inferior prope basin posticam emarginata." 



Inequivalve, foliaceous, attached by a byssus passing through 

 an opening in the side of the lower valve. Hinge with a trian- 

 gular area in each valve, that of the attached valve considerably 

 largest. Ligament on the area, and the elastic cartilage in a 

 groove in the centre of the area, terminating in the interior. 



Pedum Spondyloideum (pi. xci. f. 1 to 4.), Lam. Anim. s. 

 vert. vol. vi. p. 154. Ostrsea Spondyloidea, Gmel. no. 109. 



P. testa cuneiformi, depressa, imbricatim striata, valvae infe- 

 rioris area cardinali magna, lateribus reflexis ; colore fulvo, pur- 

 pureo nigrescente marginato. Variat albo. 



Wedge-shaped, flat, with the sides of the lower valve turned 

 upwards, and the surface striated with rows of raised points. The 

 young (fig. 2) is much shorter in proportion than the full-grown 

 shell. The smoothness of var. f. 4 is accidental. 



From the Isle of Prance. 



Plate XCI. 



Fig. 1. Pedum Spondyloideum. 



2. The same, young. 



3. White variety. 



4. Smooth variety. 



