CONCHOLOGY. 



are almost transverse. It is most proba- 

 bly a distinct species, and if so, the de- 

 signation proposed by its accomplished 

 discoverer, " Pticata," will be an excel- 

 lent one 



2. U. Pvrpureus. Shell sub-oval, some- 

 what compressed, with smaller wrinkles 

 placed between larger ones, colour dark 

 brown ; beaks placed nearer one end, 

 very carious, not prominent, generally 

 the epidermis and pearly strata are re- 

 moved, exhibiting a wax-yellow ground: 

 within reddish purple, varied with green; 

 no cavity under the beaks : teeth resem- 

 ble the preceding. 



Length, one inch* and five-eighths : 

 breadth, two inches and four fifths. 



Plate 3. fig. 1. 



This species is more numerous in the 

 rivers Delaware and Schuylkill than any 

 other of the genus : in the rivers of the 

 southern states it arrives at a more con- 

 siderable magnitude, measuring some- 

 times four inches, or more, in breadth. 

 These large specimens, and sometimes 

 the smaller ones, are a little shorten- 

 ed on the base opposite to the lamellar 

 teeth. 



, 3. U. Ovatut Shell sub-ovate, convex, 

 not remarkably thick, horn colour, not 

 radiated ; flattened and fuscus on the an- 

 terior margin ; beaks decorated, placed 

 nearer central ; umbo prominent ; with- 

 in pearlaceous ; cavity of the beaks ca- 

 pacious ; primary teeth very oblique, al- 

 most parallel to the posterior margin and 

 much compressed. 



Length, three inches; breadth, four 

 inches. 



Inhabits the Ohio river and its tributary 

 streams. 



Plate 2. fig. 7. 



4. U. Cariotus. Shell moderately thick, 

 much longer before, and shorter behind 

 the beaks ; olive green, sometimes radi- 

 ate with green, and with fine interrupted 

 wrinkles placed in longitudinal rows, but 

 usually the jjp-een radii are wanting, or 

 only visible in the anterior margin, and 

 the wrinkled radii indistinct ; in older 

 shells the middle of the base is a little 

 shortened; beaks some what prominent, 

 rather distant, carious, exposing a wax- 

 yellow surface; concavity bluish-white, 

 teeth resembling those of the preceding 

 species: but the primary ones are not so 

 much compressed or oblique ; they are 

 often sub-conic and crenate. 



Length, one inch and a half: breadth, 

 two and a quarter. 



Plate 3. fig. 2. 



Jlfusculua latior, subfuscus, Cxndeis Kne- 

 is Jtatliatits. 



Lister, conch, tab. 152, Jig. 7. 



Martini's figure of U. Piclorum resem- 

 bles this shell in outline. Vol. 6. 



Very common in the Delaware and 

 Schuylkill rivers. 



Gmelin, Ed. Syst. Nat. p. 3220, refers 

 to Lister's figure as a variety of Mya Ra- 

 diata, a native of Malabar : but we have 

 ventured to consider it a distinct species ; 

 the largest we have seen was brought 

 from Wilkesbarre by Mr. Lard. Vanuxem, 

 in length 2, breadth, 3| inches. The 

 animal is rarely infested by a parasite. 

 See the article Hydrachne. 



5. U. Ochraceus. Shell thin, fragile, 

 translucent, subovate, hinge margin 

 somewhat rectilinear, colour from a pale 

 reddish orange to a pale olive ; generally 

 radiate with dull green and with minute 

 wrinkled radii ; anterior margin very 

 finely wrinkled ; beaks decorticated and 

 approximate, with two or three small 

 concentric undulations ; within bluish- 

 white or ochraceous, tinged with red near 

 the base ; teeth very oblique and much 

 compressed. 



Length, one inch and a quarter : 

 breadth, one and three quarters. 



Plate 2. fig. 8. 



This shell, in many respects, resem- 

 bles the preceding, with which itis found, 

 but is not so obtuse in front, and is much 

 less rounded at the hinge margin, it is al- 

 so much thinner, and the beaks approach 

 each other more closely. 



6. U. JVusutus. Shell thin, oblong, 

 compressed, rostrated, horn colour or 

 fuscus, with fine crouded wrinkles, ob- 

 scurely radiate with green ; within blu- 

 ish white ; beak cavity hardly any, teeth 

 crenate. 



Length, one inch and one eighth : 

 breadth, two and three fifths. 



Very common in the Delaware and 

 Schuylkill. 



Plate 4. fig. I. 



uscw, auifustior, exaUerapar- 

 te Cuneatim prdtensus. 



Lister, conch, tab. ISl.Jlf. 6. 



7. U. Alatax. Shell moderately thick, 

 sub-triangular, generally gaping at the 

 posterior part of the base, fuscus, wrin- 



