COMCHOLOGY. 



Length, one inch and a half: breadth, 

 two and a quarter. 



Plate 3. fig. 2. 



Musculus latior, subfuscus, C&ruleis It. 

 neis Radiatus. Lister. Conch, tab. 152. 



fe-7- 



Martini's figure of U. Pictorum 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 

 Badiata, 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, 3f 

 inches. The animal is rarely infested 

 by a. parasite. Seethe article ffydrachne. 



6. 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 it is 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. 



7. U. Nasutus. Shell thin, oblong, 

 compressed, rostrated, horn colour or 

 fuscous, 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. 1. 



Musculus fuscus, auguslior, exaltera par- 

 te Cuneatim protensus. Lister. Conch, tab. 

 151. fa 6. 



8. U. Jllatus. Shell moderately thick, 

 sub-triangular, generally gaping at the 

 posterior part of the base, fuscous, wrin- 

 kled ; beaks not prominent, placed very 

 far back and decorticated ; base almost 



rectilinear ; hinge margin remarkably ob- 

 lique, rising near the termination of the 

 cartilage into an alated projection, and 

 forming almost a right angle with the in- 

 ferior slope, which is nearly equal in 

 length ; within red-purple, often with nu- 

 merous tubercles, which, upon the gaping 

 limb, are confluent ; cicatrices very 

 rough ; teeth crenate, the external lami- 

 nated one obsolete, only one in each 

 valve being very perceptible. 



Length, including the projection, three 

 inches and four-fifths ; breadth, five inch- 

 es and a half. 



Plate 4. fig. 2. 



Encyc. Meth. vol. 63, tab. 248, fig. 1. 

 a. b? 



Mr. Lesueur found this species in Lake 

 Erie, very thin and fragile. 



The specimen from which this descrip- 

 tion is taken, and also the next species, 

 were purchased by Mr. Joseph Watson, 

 at the sale of the late Professor Bar- 

 ton's collection, and by him presented 

 to the Jlcademy of Natural Sciences of 

 Pltiladelphia. There is also a specimen in 

 the Museum of Mr. Peale. 



9. U. Cylindricus. Shell very thick, 

 sub-cylindrical, emarginate before, pale 

 horn-colour varied with greenish ; hinge 

 margin undulated obliquely across the 

 wrinkles, rough on each side, rectiline- 

 ar and parallel to the base ; beaks broad 

 and prominent, with a deeply impressed 

 posterior lunule ; within perlaceous, 

 teeth thick and crenate ; cavity of the 

 beaks very deep. 



Length, one inch and three-tenths; 

 breadth, three inches and one fifth. 



Plate 4. fig. 3. 



From the collection of the late profes- 

 sor Barton ; it is said to be found in the 

 river Wabash. 



GENL'S ALASMODOKTA . 



Shell, transverse, equi valve, inequila- 

 teral ; hinge with a primary tooth in each 

 valve ; cicatrices three. 



Animal resembling that of Unio ? 



1. Marginata. Shell transversely ob- 

 long sub-oval, white, covered with an 

 olive brown epidermis, obsoletely radiate 

 with green, numerous concentric wrink- 

 les ; umbo with about three concentric 

 undulations ; ligament slope abruptly de- 

 pressed, with numerous, obtuse, oblique 

 rugae, decussating the concentric ones, 



