229 



Unio manubius. T. transversa, elongata, subarcuata, subven- 

 tricosa, anlice angustata, postice acuta, margine dorsali arcuato 

 in marginem poslicum desinente ; disco rudi, epidermide nitido- 

 corneo induto ; dentibus cardinalibus compressis, triangularibus, 

 ad marginem fere parallelis, d. lateralibus remotis, arcuatis ; 

 margarita argentata, talcosa. Long. 3^ ; alt. l^ ; lat. 1|- poll. 

 Chihuahua, sixty miles from Camp Ringgold. By Dr. T. H. 

 Webb. 



Allied to U. declivis^ Say = geometricus, Lea, in which the 

 posterior extremity is recurved and angular, rather than de- 

 curved with rounded angles ; and the surface is dead and dusky. 

 In our shell, the anterior extremity is more prolonged, and 

 much more slender. It is also intermediate between U. ohesus. 

 Lea, and U. camptodon, Say. 



Anodon horda. T. tenuis, transversa, elongato-ovata, ven 

 tricosa, dilute cornea, viridi nubeculata, antice angustata, suba 

 cuta, postice subtruncata, dorso excavato, declivitate umbonal 

 obtuse angulato, submarginato, umbonibus obtusissimis, pallidis 

 tenuiter undulatis, ad trientem anteriorem sitis ; margarita ar 

 gentea. Long. 3^ ; lat. 1^ ; alt. If poll. Comanche Creek 

 Texas. Dr. T. H." Webb. 



Remarkable for the broad, inflated, pale beaks, presenting no 

 distinct apex. In size and form, it might, at first sight, be taken 

 for U, anodontoides. It approaches to A. ferruginea and A. 

 Dunlapiana, but differs in its proportions. 



Cyclas nobilis. T. magna, solida, ovato-rhomboidea, 

 utrinque truncata sed postice obliquius ; umbonibus anticis ; 

 tumidis ; margine dorsali utrinque arcuatim declivibus ; mar- 

 gine ventrali arcuato ; valvis remote et profunde sulcatis ; epi- 

 dermide flavescente ; dentibus cardinalibus minimis ; intus pal- 

 lida. Long. ^ ; lat. -^ ; alt. f poll. Found near San Pedro, 

 California. Dr. Webb. 



Has a general resemblance to what is usually regarded as 

 C similis, but is more solid, more inequilateral, more obliquely 

 truncated posteriorly, beaks more conspicuous, color paler, 

 grooves coarser, cardinal teeth less developed. C. solidula. 

 Prime, must also nearly correspond in its characters. 



