218 PROCEEDINGS OF THE MALACOLOGICAL SOCIEXr. 



M. Galloprovmcialis, Lamk. 



M. ungulatus, Linn, {non Lamk.). 



M. Orunerianus, Dunker. 



M. Dunkeri, Eeeve {— Grmjanus, Dunker). 



M. latissimus, Clessin. 



M. planulatus, Lamk. 



M. Californicus, Conrad. 



M. horealis, Lamk. 



M. crassitesta, Lischke. 



M. Patagonicus, d'Orb, 

 Chloromya, Morch. Umbones more completely terminal, and the 

 anterior side inflexed so as to form a small hinge-plate below the umbo. 

 Shell always smooth. Riblets of anterior side short, and sharply 

 inflexed beneath umbo. Teeth 1-2 or 2-2 ; most frequently the 

 former, but the single tooth is sometimes in the right, sometimes in 

 the left valve. No anterior adductor scar, byssal scars three, an 

 anterior, a median, and a posterior, the latter united to the posterior 

 adductor. Type, M. ferna, Linn. 



To this group belong the following species : — 



M.pictus, Born (= M. afer, Gmel.). 



M. latus, Chemn. 



M. variegatus, Chemn. (= J/". aeJiatinus, Lamk.). 



M. smaragdinus, Chemn. 



M. meridionalis, Krauss. 



M. Taprohanicus, Blanf . 



M. palliopunctatus, Dunker. 



M. chorus, Molina. 

 Aulacomya, Miirch. Shell always ribbed or furrowed. Umbones 

 terminal, elongated, and often projecting beyond and in front of the 

 anterior side, which has only a single riblet twisted in under the 

 umbo. Ligament long and carried in a channel beneath the umbones. 

 Hinge without definite teeth, but having a tooth-like ridge in one 

 valve which fits into a groove or depression in the other valve. 

 Anterior adductor often absent, but other scars as in Eumytilus. 

 Type, 31. Ilagellanicus, Chemn. 



The only other species that I have seen which can be included in 

 this section are : M. deciissatus, Lamk., M. crenatiis, Chemn., and 

 perhaps the rare M. ohhngus, Clessin. 



It will be convenient to consider the genus Modiola next, before 

 passing on to the other species which possess posterior crenulations 

 as well as anterior teeth. I have elsewhere ^ given my reasons for 

 holding to the Lamarckian name of Modiola (or Modiolus), and for 

 rejecting that of VoUella of Scopoli. The following will serve as 

 a definition of the Modiola shell. 



Genus Modiola, Lamarck. 

 Shell oblong or elongate, oblique, generally inflated toward the 



1 Journ. Couch., vol. xi, p. 101 (1904). 



