328 



et prope ligamentum magnum inciso; extremitate antica rotun- 

 data ; costa umbonali magis mimisve conspicua ; dentibus prima- 

 riis distinctis ; margine cardinali sub ligameiito intus incrassato, 

 superficie interna impolita. 



Testa seniore obovali, sequilaterali ; margine dorsali subhorizon- 

 talij convexiusculo ; latere antico lato ; extremitate postica obtusa ; 

 margine postico angulum obtusum ciim margine ventrali formante ; 

 ligamento maximo. 



Tedd junior e sicut in seniore^ sed ovali, insequilaterali ; margine 

 dorsali antico subdeclivi : latere antico longiore, attenuato. 



Yar. Testa ovali, inpequilaterali, margine dorsali antico subde- 

 clivi ; latere antico longiore, plerumque ad extremitatem attenuato ; 

 extremitate postica angulata; margine ventrali postice subincur- 

 vato et magis sursum acclinato. 



Inequivalve, tolerably strong, smooth, glossy, rounded in front ; 

 one valve convex, the other flattened ; ventral margin subarcuated ; 

 dorsal edges not greatly sloping, near the large hgament (under 

 wliich the hinge margin is internally thickened) with an incision ; 

 umbonal ridge more or less conspicuous ; teeth distinct. 



Adult. Oboval, equilateral, hinge-margin subhorizontal and 

 slightly convex; anterior side broad; hinder extremity obtuse; 

 posterior edge forming one obtuse angle with the ventral ; hgament 

 very large. 



Young. EesembHng the adult, but oval and inequilateral ; the 

 front dorsal edge moderately sloping; anterior side the longer, 

 attenuated at its termination. 



Var. Oval, inequilateral ; front dorsal edge moderately sloping ; 

 anterior side the longer, and generally attenuated at its extremity ; 

 posterior end angulated, the hinder ventral edge being somewhat 

 incurved and sloping upward. 



California. 



To this section belong, Hkewise, the T. lateralis and irevifrons 

 of Say, which, however, I am unable to identify ; and as the species 

 have not been recognised by any subsequent conchologists, and 

 are unknown even to the naturahsts of the United States, I 

 cannot, consequently, add to descriptions which will not exactly 

 apply to any TeUens I am acquainted with. 



" Tellina lateralis, Sai/, Journ. Ac. Nat. Sci. Phdad. 

 Transversely subovate, subequilateral ; posterior (anterior) mar- 



