FREE INSTITUTE OF SCIENCE 

 TERTIARY FAUNA OF FLORIDA 



closely allied group with /'. pcsfdis L. as the type; and Bucquoy, Dautzen- 

 bcrg, and Dollfus (1889) propose l\-plinn, with /'. clavatus Poli as type, which 

 would include such species as /'. panamensis ; and Sacco adds Flexopecten 

 (1897) for P.flexuasus Poli, which differs by having larger ears. 



Snbgenus Pscitdmiiiisiiun H. and A. Adams, 1858. Type Pecten exoticiis 

 Chemn., = /'. pseudamusium (Klein) Sby. 



Shells small, thin, more or less translucent; the sculpture, if any, feeble; 

 inner face of the disk without lirae ; disk with or without Camptonectes stria- 

 tion, frequently with concentric imbrication. 



Section Pseudamusium s. s. Type P. psevdamttstum Sby. (== exoticiis Chemn., 

 etc.). 



Sculpture discrepant on the two valves, the right valve having the con- 

 centric, and the left valve the radial elements most pronounced ; valves usually 

 flatfish or compressed. The type is a shallow-water species and shows bright 

 colors ; the species from deep water are frequently pale or whitish. The latter 

 have been separated as Cyclopccten by Verrill. 



Section Camptonectes (Agassiz MS.) Meek, 1864. Type P. lens Sby. 



Shell similarly sculptured on both valves, more or less inflated; smooth, con- 

 centrically more or less undulated, divaricately striate, or delicately imbricated. 



The minute features of surface sculpture are so interchangeable and so 

 variable that I cannot regard them as having sectional, much less generic, 

 value, at least in the sense in which the term is used in this work.* 



Though Cainptotiectes was originally based on the character of the 

 divaricate stria:, the species in which this character is obsolete must be 

 included, unless violence is to be done to what seems close relationship. 

 Syncydonema Meek, if correctly made out by that careful author, has a com- 

 pletely closed shell without a byssal notch, the ears subequal, the left valve 

 smooth, the right concentrically striated. 



* Professor Verrill proposes forllic smooth form Pi'dinclhr ; for the undulated form Hyalopecten ; 

 the divaricately sculptured shells would then he typical Camptonectes; the imbricated ones like P. 

 vitrcus [(Gmelin, 1792) Dillwyn, 1817 (-)- aculeatus JelTr., 1843, -f abyssorum Loven, ; gcni.'llaro-filii 

 1'iiondi) not P. vilrftis Gray, 1824 ( I', gronlandicus Sby., 1843) ; P. vitreus Risso, 1826 ; P. -jilrcus 

 Kiii<;, 1831 ( /'. corneiis Sby., 1843), nor P. vitrms Sby., 1843] would be Palliolum Monts. 

 (restr.), 1884. Eburneopecten Conrad, 1865, based on P. sdnlil/iilus Conr., is an exact synonyme of 

 Camptoncctes. Lissochlamis Sacco (1897) is founded on P. e.rcisus Bronn (non Pusch), a species 

 unknown to me. 



