JUKES-BROWNE : SYNOPSIS OF THE VENEKIDJE. 85 



Genus GoMPHiNA, Morch, 1853. 



The isolation of Gomphina as a genus was discussed and maintained 

 bv me in 1909,' and at the same time it was pointed out that the 

 small group of shells now known as Lioci/ma seemed to stand in the 

 relation of a sub-genus. Since then I have ventured to affiliate 

 the small American shells called Psephis by Carpenter in 1864, but 

 renamed Psephidia by Dr. Dall in 1902. and I have also described 

 a new sub-genus under the name of Aeolus, based on a species from 

 the Falkland Islands which was referred to PsepJiishy Messrs. Preston 

 and Cooper in 1910.- The species of Gomphina proper are only 

 found on the western side of tlie Pacific Ocean from Australia north- 

 ward to Japan, and the other groups are entirely American. 



Generic characters : Shell trigonal or oval, solid, smooth or con- 

 centrically striated. Lunule flat, circumscribed. Escutcheon not 

 defined. Valve-margins smooth or tangentially grooved. Kight 

 posterior and left anterior dorsal margins grooved to receive the 

 opposite bevelled margins. Hinge-plate short and triangular ; teeth 

 equally divergent, and both medians generally grooved. Pallial 

 sinus small. Pedal scar separate from that of the adductor. 



Gomphina, s.s. Type, Venus donacina, Chem. 



Shell trigonal, smooth, and near equilateral. Three teeth in each 

 valve, the left posterior confluent with the nymph, and sometimes 

 rugose, as also the right nymph. Pallial sinus short and rounded. 



Suh-genera. 



Psephidia, Dall. Type, Psephis lordi, Baird. 



Shell small, smooth, sub-equilateral. Left posterior tooth free. 

 Inner margins tangentially grooved and microscopically crenulated. 

 Pallial sinus short, triangular. 



Aeolus, Jukes- Browne. Type, Psephis foveolata, Preston & Cooper. 



Shell small, trigonal, equilateral. Teeth 3 in the left valve, 2 in 

 the rig]:t. Ventral nuirgins smooth, but dorsal nuirgins striated. 

 Pallial line very slightly inflected. 



Liocyma, Dall. Type, Venus fluduosa, Gould. 



Shell oval, inequilateral, oblique, concentrically striated. Three 

 teeth in each valve. Pallial sinus short and rounded. Valve-margins 

 smooth. 



Genus Clementia, Gray, 1842. 



Animal having long siphons, united for their whole length, with 

 plain orifices. Foot compressed and sub-quadrate (or hatchet-shaped) 

 like that of Dosinia. ^laiitle-margins plain. 



Shell oval or oblong, convex, thin or substantial, sculpture 

 generally concentric and feeble, but sometimes reticulate. Lunule 

 indefinite or feebly defined. Escutcheon generally depressed, but 

 not defined. Valve-margins smooth, and right posterior dorsal 

 margin grooved. Hinge-plate weak or strong in relation to the 

 thickness of the shell, with a concave expansion in front of the teeth ; 



' See Proc. Malac. Soc, vol. viii, p. 233. 



■^ See Ann. Mag. Nat. Hist., vol. xii, p. 479, 1913. 



