TRANSACTIONS OF WAGNER 

 698 



TERTIARY FAUNA OF FLORIDA 



Until more is known, this section would best be retained. It is doubtful 

 how important the characters of Eiitolimn Meek (1864) may prove to be. 

 Lissppecten Verrill (1897) based on P. hyalmus Poli seems to me merely a 

 somewhat degenerate j^quipectoi. Leptopcctcn of the same author is based 

 on the kelp-inhabiting variety of P. {Clilainys) latiaiiritus Conrad; its peculi- 

 arities result directly from its special situs ; the shells intergrade perfectly with 

 the other chlamydoid forms. 



Subgenus Amusuim Bolten, 1798. Type P. pletironcctes L. 



Valves flattish, internally lirate, externally usually smooth or faintly 

 striated; ears subequal ; the ctenolium absent and the byssal notch obsolete. 

 Pleuronectia Swainson, 1840, is synonymous. 



Section Amusium s. s. Type P. plciironectes L. 



Valves about equally convex, gaping at the sides, nearly similar in sculp- 

 ture, the recent forms having the left valve darkly colored and the right valve 

 pale or albescent. 



Amiisium Lyoni Gabb in the youthful condition has a sculptured left valve 

 like Propeavuishuii. 



Section Propeanmsium Gregorio, 1883. Type P. mcgidsculph/s Tiberi 

 (= fenestratus Forbes). 



Right valve impressed about the distal margin, which is not fully calcified, 

 partially concave, the sides partially closed, away from the ears ; the lirje 

 shorter; the external sculpture chiefly concentric, while on the left valve, if 

 present, it is radial ; the recent forms usually glassy or pale colored in both 

 valves. 



On anatomical grounds Professor Verrill separates, as Paraiiiushim, Amu- 

 sium Dalli Smith ; but there are no distinctive conchological characters. 



In the Bulletin of the Zoological Museum of the University of Turin, 

 No. 298, pp. 101-2, June 11, 1897, Sacco has given a list of subdivisions of 

 Pecten, without definition, but referring to the species he regards as types, or 

 includes under the several subgenera. Among those not above mentioned 

 are the following : Under the genus Amusium, of which P. cristatus Bronn is 

 regarded as typical, Paruiarnussiuni Sacco (1897) is typified by P. duodecivila- 

 mellatus Bronn, and Variamussium Sacco (1897) by P. cancellaliis "Schmidt" 

 (? Goldfuss, not Bean and Phillips or McCoy), while P. fenestratus Forbes is 

 included. This section is therefore a synonyme of Propeamusium de Gre- 

 eorio, 188^. 



