908 PSOCEEDINGS OF THE NATIONAL MUSEUM. 



plate wide, nearly straight, set with strong, irregular, taxodont teeth 

 throughout its length; beak cavities moderate, with a row of dorsal 

 scars running obliquely downward and forward; anterior and posterior 

 muscle scars well defined. 



Animal with the palpi semilunar, united to the mantle by a straight 

 border, longer than wide; outer gills generally larger than the inner, 

 united their whole length to the mantle; inner united to the abdominal 

 sac ; genitalia occupying each side the lateral part of the visceral mass as 

 far forward as the foot; mantle closed below the branchial siphon, and 

 united into branchial and anal siphons; anal opening rather small; 

 branchial openinglarge, the two separated by a solid bridge which solders 

 together the extremities of the four branchite; both orifices have a 

 thickened inner edge, the branchial being furnished with short tubercles 

 or granules; mantle united below posteriorly one-fourth its length j 

 foot large and strong; adductor muscles strong (Pelseneer). 



Subgenus PLEIODON Conrad. 



Characters as in the genus. 



t PLEIODON OVATUS Swainson. 



^ Iridina ovata Swainson, Phil. Mag., LXI, 1823, p. 112.—' Oken, Isis, 1834, p. 

 458.— "Reeve, Coucli. Syst., 1, 1841, p. 122, pi. xciii.— *Hanley, Biv. Shells, 

 1843, p. 225. — 'Catlow and Eeeve, Conch. Nom., 1845, p. 68; * Elements of 

 Conch., II, 1860, pi. xxxiii, fig. 184. — *Clessin, Conch. Cab. Ano., 1875, p. 

 230, pi. Lxx, fig. 2; lxxi, fig. 2. 



* Platiris {Iridina) ovata Lea, Syn., 1838, p. 33; 1852, p. 54; 1870, p. 88. 



* Pleiodon ovata Conrad, Jl. Ac. Nat. Sci. Phila., VII, 1854, p. 298; * H. and A. 



Adams, Gen. Rec. Moll., 11, 1857, p. 506. 

 "^ Pleiodon ovatiis Chenu, Man., 1859, II, p. 148, fig. 728.— * Sowerby, Conch. 



Icon., XVI, 1866, pi. i, fig. 1. -*P^tel, Conch. Sam., Ill, 1890, p. 188. 

 Iridina exotica Children, Brando's Jl., XV, 1823, p. 1 

 ""Pleiodon macmurtriid Conrad, ,11. Ac. Nat. Sci. Phila., VII, 1834, p. 13, pi. xiii; 



VII, 1854, p. 298. 



* Margarita, {Phiodon) macmurtriei Lea, Syn., 1836, p. 55. 



* Iridina valeus Jay, Cat., 1850, p. 70.' 



*Mutela valeus H. and A. Adams, Gen. Rec. Moll., II, 1857, p. 506. — * P/etel, Conch. 



Sam., Ill, 1890, p. 187. 

 "" Platiris {Iridina) leaii'L^A, Syn., 1852, p. 54; 1870, p. 88.^ 

 ^ Pleiodon leaii H. and A. A.dams, Gen. Rec. Moll., II, 1857, p. 506. — *PiETEL, 



Couch. Sam., Ill, 1890, p. 188. 

 "" Pleiodon splendens Conrad, Jl. Ac. Nat. Sci. Phila. , VII, 1854, p. 299. 



* Iridina splendida Chenu, 111. Conch., 1858, pi. i, figs. 2, 2a, 26, 2c, 2d. 



West Africa. 



The following are unflgured species of Pleiodon: 



* Pleiodon diolibanus Bourguignat, Moll. Egypt and Ah., 1879, p. 47. 



* Pleiodon elongatus Bourguignat, Moll. Egypt and Ab., 1879, p. 47. Senegal River. 



' Said to be of Parreyss. 



"Presented to Dr. Lea by Sowerby as Iridina leaii. Lea believes it to be a young. 

 ovatiis. 



