104 KELLIADJ5. 



GALEOMMA. Turton. 



Shell thin, transversely oval, equivalve, subequilateral, 

 gaping widely in front ; its surface longitudinally striated 

 and decussated ; beaks minute, acute ; cartilage pits under 

 the beaks, small ; no hinge teeth ; ligaments internal. 

 Pallial impression simple, muscular scars unequal. 



Animal oval, mantle very large, double margined, tuber- 

 culiferous ; closed in front ; siphonal openings posterior, 

 two. Foot long, ligulate, byssiferous, perforate, projecting 

 from an anterior opening of the mantle ; two pair of 

 branchial leaflets ; mouth with large lips and developed 

 labial palps. 



This very curious genus was first made known by Tur- 

 ton in 1828. The same species was afterwards strangely 

 described as a Hiatella by Costa, and an antarctic form 

 was figured in one of the French voyages as a Psammobia. 

 Its true systematic position has been much disputed. 

 That, however, it has no affinities with the Tubicolee or 

 Tellinidce a glance at either shell or animal will suffice, and 

 it seems strange that conchologists of experience should 

 ever have so placed it. Its true position is unquestionably 

 about where we now introduce it, viz. as a link between 

 the Kelliadce and the Arcada. With the latter family its 

 alliances have been clearly shewn by Mr. Clark. M. 

 Mittre holds that it is closely connected with the Tridac- 

 nid<£, and should form the type of a family parallel with 

 that tribe. 



