PEDUM. 219 



or organ of attachment of the class of shells called in the system 

 of Lamarck "Pedunculated Cirripedes," consisting of a fleshy 

 tendinous tube, by the lower end of which they are attached to 

 sub-marine substances. 



PEDICULAMA, Sw. A genus of " Scutibranchia," thus de- 

 scribed: " Shell irregular, sub-patelliform ; a thick, large, obsolete 

 apex on one of the longest sides, and an internal callous rim 

 within, on one side only ; circumference undulated, irregular. P. 

 Sicula, Sw." Sw. p. 357. Sicily. A singular shell of the nature 

 of Calyptrsea, which is found attached to corals, conforming its 

 shape to the irregularity of their surface, and fitting closely. Ex. 

 Fig. 513. 



PEDIPES. Adanson. Fain. Auriculacea, Bl. Colimacea, Lam. — 

 Descr. Sub-globose, longitudinal, thick, striated ; spire equal to 

 the aperture in length ; aperture sub-ovate ; peritreme sharp, 

 thickened within, modified by the last whorl ; columella with 

 three strong plaits on the inner edge ; outer lip with one fold. 

 — Obs. This genus contains but one or two small recent species, 

 which in some respects resemble Auricula, from which it is 

 known by the thickness of its shell, and its globular form. Fig. 

 299, P. Adansoni. Coast of Africa. 



PEDUM. Lam. {A shepherd's crook.} Fam. Pectinides, Lam. 

 Sub-ostracea, Bl. — Descr. Irregular, inequivalve, sub-equilateral, 

 attached by a byssus passing through a sinus in tbe lower valve ; 

 hinge toothless, with a triangular area in each valve, separating 

 the umbones ; ligament contained in a groove running across the 

 area ; muscular impressions one in each valve, large, sub-orbicu- 

 lar ; both valves flat, narrow at the dorsal, broad at the ventral 

 extremities ; lower valve with raised edges overwrapping the 

 upper. — Obs. This singular genus, of which only one species is 

 known, differs from Ostrea, not only in shape and structure, but 

 also in the mode of attachment, which is by means of a byssus 

 passing through the lower valve, in Pedum, but by a portion of 

 the outer surface of the shell in Ostrea. P. Spondyloideum 

 (fig. 179) is the only species at present known. Moluccas. 



