NO. 1 SOOT-RYEN : THE FAMILY MYTILIDAE 95 



Subgenus Diberus is recorded from the Lower Miocene, Tampa, 

 Florida (Dall, 1898, "Oligocene"), and the recent species occur in the 

 warm and tropical seas on the east and west coasts of America, the Red 

 Sea east to the Philippine Islands and Australia. 



The west American species is well known as Lithophaga plumula 

 (Hanley) 1843, with the variety kelseyi Hertlein and Strong 1946. 

 Reeve, in Conchologia Iconica, has described Lithodomus subula from 

 an unknown locality. The short description and figure 26 of Plate 4 

 seem to agree completely with the form named kelseyi by Hertlein and 

 Strong. Lithodomus pessulatus Reeve 1857, also described from a speci- 

 men without locality, has vertical wrinkles on the anteroventral part of 

 the valves. It will therefore be easily known if it should be found on the 

 west American coast. 



Lithophaga canalifera (Hanley) 1843 is considered a Diberus by 

 Lamy (1937) and is here included in this subgenus, although the pattern 

 of the incrustation is different. Lamy (1937) mentions Lithophaga 

 abbotti Lowe in connection with species of Diberus, but according to the 

 description it is not a Diberus. 

 Key to the west American species : 



1. Incrustation with strong radiating grooves 



without a featherlike pattern canalifera (Hanley) 



Incrustation with a featherlike pattern 2 



2. Shell rather high, more than 30% of length 

 including incrustation ; posterior adductor 

 scar near posterior margin ; at most its own 

 length from the margin; incrustation dis- 

 tinctly like a feather with elevated ribs plumula (Hanley) 

 Shell lower, height about 25% of length in- 

 cluding incrustation, posterior end more 



tapering; posterior adductor distinctly more 

 than its own length from posterior margin; 

 incrustation irregular and lower subula (Reeve) 



Lithophaga (Diberus) canalifera (Hanley) 1843 



Text-fig. 78 



Modiola canalifera Hanley, Catalogue of Recent Bivalve Shells, 1843, 



p. 239, PI. 24, fig. 22. 

 Syn.: f Lithophaga appendiculata (Philippi) Tomlin 1928. 

 Holotype: British Museum. 

 Type loc: South America. 



