589. truncatosa, Mich. 



590. tuberculatus, Bar. 



591. tuberculatus, Fir. 



592. tuberculosa, Valen. 



593. tuberosus, Lea. 



594. tumescens, id. 



595. tumidus, Retz. 



596. turnidulus, Lea. 



597. tumulatus, Mori. 



598. turgidus, iea. 



599. Turtonii, Fayr. 



600. Tuomeyi, Lea. 



601. umbrosus, zW. 



602. undulatus, Bar. 



603. undulatus, Ze«. 



604. unicolor, ^rf. 



605. uniformis, Sow. 



606. Urii, Z7m. 



607. utriculus, Lea. 



608. Valdensis, Himrf. 



609. Vanuxemensis, Lea. 



610. variabilis, id. 



611. varicosus, «/. 



612. Vaughanianus, id. 



613. ventricosus, Z^ar. 



614. venustus, ira. 



615. Verreauxianus, id. 



616. verrucosus, J?«r. 



617. vibex, Con. 



618. viudiflavus, A"«s£. 



619. Yoltzii, Koch. 



620. Watereensis, Lea. 



621. Wheatleyanus, z'e?. 



622. Whiteianus, id. 



623. Woolwichii, JZore. 



624. Zeiglerianus, Lea. 



625. Zeyheri, Menke. 



626. zigzag, Zm. 



627. Zimerrnani, Steutz. 



Figure. 



Unio tuberculatus. PI. 33. Pig. 183. Shell, showing strongly de- 

 veloped lateral and cardinal teeth, the latter of which is striately 

 grooved. 



Genus 2. HYRIA, Lamarck. 



Animal ; similar to that of Unio, but with the posterior orifices 

 prolonged into siphons. 



Shell ; obliquely triangularly auriculated on each side ; hinge 

 composed of two lateral teeth, the anterior in each value, elon- 

 gated, the posterior multipartite, approaching the form of a 

 cardinal tooth. 



The genus Hyria, which corresponds to Mr. Lea's subgenus Triquetra, 

 has been limited until lately to three species, natives of South America, in 

 which the animal has its posterior orifices, according to Dr. Gray, pro- 

 longed into siphons, whilst the shell is characterized by a peculiar obliquely 

 triangular form, eared on each side, with a hinge of two lateral teeth, of 

 which the anterior is much elongated, whilst the posterior is much shorter 

 and has more the form of a cardinal tooth. In 1857 Mr. Lea referred to 

 this genus a curiously twisted elongated Naiad from China, H. contorta, 

 but this shell appears to me to be very far removed from the South Ame- 

 rican type. 



