NO. 1 SOOT-RYEN : THE FAMILY MYTILIDAE 99 



Distribution : La Jolla, California, to Peru, Atlantic : West Indies, west 

 Africa, Mediterranean; Red Sea; Australia; Japan. 



Subgenus LABIS Dall 1916 



Labis Dall, Proc. U. S. Natl. Mus., vol. 52, 1916, pp. 405-406. 

 Type of subgenus: Lithophaga attenuata Deshayes 1836 (monotypy). 

 Remarks: This "Section" was described for attenuata alone, character- 

 ized by the "smooth appendage of which the distal end is internally flat- 

 tened and somewhat separated from the appendage of the opposite valve, 

 the ends being rounded." It seems useful to include Lithophaga cu/ningi- 

 ana (Reeve) 1858 and Lithophaga peruviana (Orbigny) 1846 in the same 

 subgenus, as proposed by Lamy (1937). The main characteristic of Labis 

 will then be the smooth appendage projecting beyond the posterior mar- 

 gin of the valve. The anterior retractor seems also to be shorter and 

 broader than in the other Lithophaga species. 



Species of this group are restricted to the west coast of Central and 

 South America and Australia, where Iredale's (1939) section Doliolabis 

 seems to be identical. 

 Key to the west American species : 



Projecting posterior part of the incrustation 



long, rounded apically attenuata (Deshayes) 



The projecting posterior part of the incrus- 

 tation short, with a median spine peruviana (Orbigny) 



Lithophaga (Labis) attenuata (Deshayes) 1836 

 Plate 10, fig. 57; text-fig. 77 



Modiola attenuata Deshayes, Animaux sans Vertebres, ed. 2, vol. 7, 



1836, p. 28. 

 Syn.: Lithodomus inca Orbigny 1846. 

 Holotype: ? 

 Type loc: Peru and Chile. 



Remarks: The incrustation on the ventral side is sometimes arranged in 

 vertical rows ; the posterior projection of the incrustation is sometimes 

 long, up to 20 mm, sometimes very short, but always without a median 

 ridge; the inside of the projection is more or less hollowed out, forming 

 a median cavity when the valves are closed. The median incrustation 

 often has a pattern of radiating but not divaricating lines and the edges 

 of the projecting part are irregularly granulated. There seem to be two 

 different forms, an elongate slender one and a shorter thicker one, which 

 apparently occur in different localities. 



