Occasional Papers of the Museum of Zoology 49 
Unio biangularis Lea, ’40, p. 288. 
Unio biangulatus Lea, ’42, p. 197, pl. 9, f. 8. 
Lampsilis biangularis (Lea), Simpson, “14, p. 59. 
Lampsilis perdix (lea), Simpson, ’14, p. 88. 
Nephronaias pectorosa (Con.) =U. perdix Lea=U. biangularis 
Lea = U. biangulatus lea = (possibly) U. vittatis Raf., Ortmann, ’18, 
p. 560. 
U. vittatis Raf. would have priority, if identifiable. Its shell 
is oval and has been compared by Rafinesque with L. fasciola 
Raf., but is said to be larger, rounder, with straight rays. 
This does not fit pectorosa, which surely is not “rounder” than 
fasciola, and there are additional characters in the original 
description which cannot be reconciled with pectorosa, chiefly 
“2 or 3 oblique ribs.” U. vittatis is not identifiable. 
It has been questionably referred to inflatus and siliquoideus 
Bar. by Conrad (34, p. 69). 
The identity of Conrad’s and Lea’s species is evident to any- 
one familiar with this form, and the preference of perdix by 
Simpson is due only to the incorrect date given for it. Already 
Conrad (’36) has claimed his species and has quoted the cor- 
rect dates. . 
Genus TRUNCILLA Rafinesque, 1819 
Type: Truncilla truncata Raf. 
Truncilla Rafinesque, ’19, p. 427; "20, p. 300 (no type named) ; Herr- 
mansen, "40, p. 627 (type, Truncilla truncata Raf.). 
Amygdalonatas Crosse and Fischer, ’93, p. 557 (type, U. cognatus 
Lea) ; Simpson, ’00, p. 604; Ortmann, 712, p. 327. 
Since Tr. truncata Raf. (= elegans Lea) is supposed to be 
congeneric with U. cognatus Lea, and since Herrmannsen has 
designated truncata as the type of Truncilla, this name will 
have to be used for the present genus superseding that of 
Amygdalonaias. 
This will necessitate a change in the name of the genus which 
has been usually called Truncilla. See under Dysnomia. 
