294 MANUAL or IHE MOLLUSCA. 



2.2, one of them small; a ijosterior lateral tooth in each valve; ligament 

 external ; muscular impressions oval ; paUial line simple. 

 Fossil, 11 sp. Lias — Bath Oolite. Brit. France. 



DiPLODONTA. Bronn. 



Etym. DipJos, twin, odonta, teeth. S>/n. Sphserella, Conrad. 



Type, D. lupinus ( Venus) Brocchi. PI. XIX. fig. 9, 



Shell sub- orbicular, smooth ; ligament double, rather long, sub-marginal ; 

 hinge-teeth 2.2, of which the anterior in the left valve, and posterior in the 

 right, are bifid ; muscular impressions polished, anterior elongated. 



Jtdfnal with the mantle-margins nearly plain, united; pedal opening 

 large, ventral ; foot pointed, hollow ; palpi large, free ; gills 2 on each side, 

 distinct, the outer oval, inner broadest in front, united behind ; branchial 

 orifice small, simple ; anal larger, with a plain valve. 



Dislr. 12 sp. W. Indies, Rio, Brit. Medit. Red Sea, W. Africa, India, 

 Corea, Australia, California. D. diaphana (Felania Recluz) burrows in sand. 



Fossil, Eocene — . U. States, Europe. 



? Scacchia, Philippi, 1844 ; Tellina elliptica, Sc. Shell minute, ovate, 

 posterior side shortest ; hinge-teeth 1 or 2, laterals obsolete ; ligament mi- 

 nute; cartilage internal, in an oblong pit. Animal with mantle widely 

 open ; siphonal orifice single ; foot compressed, linguiform ; palpi moderate, 

 oblong. Distr. 2 sp. Medit. Fossil, 1 sp. Pliocene, Sicily. 



? Cyamium, Philippi, 1845, C. antarcticum, PL XIX. fig. 16. Shell 

 oblong, hinge-teeth 2.2 ; ligament double; cartilage in a triangular groove 

 behind the teeth in each valve. Distr. Patagonia. 

 Ungulina, Daudin. 



Etym. Ungulina, like a hoof, Type, U. oblonga. PI. XIX. fig. 10. 



Shell sub -orbicular ; ligament very short ; epidermis thick, wrinkled^ 

 sometimes black; hinge-teeth 2.2 ; muscular impressions long, rugose. 



Animal with the mantle open below, fringed ; siphonal orifice single ; 

 foot vermi-form, thickened at the end and perforated, projecting from the 

 base of the shell or folded up between the gills ; palpi pointed ; gills 2 on 

 each side, unequal, the external narrower, with a free dorsal border, inner 

 widest in front. 



Distr. 4 sp. Senegal, Philippines, excavating winding galleries in coral. 

 Kellia, Turton, 1 822. 



Etym. Named after Mr. O'Kelly of Dublin. 



Syn. Lasea (Leach) Br. 1827- Cycladina (Adansonii) Cantr. Boruia 

 (sub-orbicularis) Phil. Poronia (rubra) Recluz (not Willd.) Eryciua (cycla- 

 diformis) Desh. (not Lam.) 



Types, K. sub-orbicularis. Mont. K. rubra. PI. XIX. fig. 12. 

 Shell small, thin, sub-orbicular, closed ; beaks small ; margins smooth ; 

 ligament internal, interrupting the margin (in K. suborlicularis), or on 



