574 UNIO 
clopedie Methodique (pl. 248, fig. 3) are what we understand 
as U. batavus, the latter being the one cited by Lamarck. 
Lamarck does not figure his species, but refers to pl. 
cexivi, fig. 3, in the Enclycopedie Methodique, which is the 
species commonly known as Unio batavis. 
This is a very abundant, widespread ‘and variable form. 
Every shade of variation long ago received a specific name 
and all these have been renamed again and again by the mem- 
bers of the new school of conchology. The species has been 
repeatedly confounded with the much rarer Margaritana crassa, 
which is a larger, ruder and more arcuate form. 
Ortmann, (1. c.), follows Thiele. (Suessw. Fauna Deutsch., 
19, 1900, p. 35). in considering the U. crassus Retz. to be this 
species. He also follows Haas, (1. c.), in giving priority to 
musivus Speng. over batavus 1am. According to Haas, (1. ¢.), 
the batava of Maton and Rackett is not the same as Lamarck’s 
species of that name, but is probably a form of pictorum, as 
this species is not found in England. 
Section CAFFERTA Simpson, 1900. 
Cafferia Simpson, Syn., 1900, p. 824. 
Shell elongated or elliptical, rhomboid when old, solid; beaks 
full, the sculpture corrugated zigzag, the ridges often extend- 
ing over the disk; epidermis yellowish-brown to nearly black, 
dull colored, somewhat sulcate; teeth rather strong; muscle 
scars deep, well defined. 
Type, Unio caffer Krauss. 
Since the publication of the Synopsis I have had the oppor- 
tunity of examining gravid specimens of a member of this 
section and find that it is a Unio. 
Group of Unio caffer. 
Characters as in the section. 
UNIO CAFFER Krauss. 
Shell somewhat elongated, subrhomboid, the posterior point 
often drawn downward in old shells, solid, subinflated to in- 
flated, inequilateral; beak sculpture zigzag, the beaks being 
