CONCHIFERA. 
FAMILY V.—IRIGONIADZ. * 
? IscHyRinA, Billings, 1866. 
Type, I. Winchelli, Billings. 
Shell equivalve, inequilateral, two strong ridges radiating 
from the beak in the interior of each valve. 
Fossil, 2 species. L. and M. Silurian. Anticosti. 
FamiIty VI.—UNIONIDA.t 
ANTHRACOSIA, King, 1856 (see p. 470). 
Etymology, anthrax, carbon, in allusion to the carbonaceous 
deposits in which the genus is usually found. 
Type, A. Beaniana, King. Coal Measures, Newcastle. 
Shell equivalve, inequilateral. Teeth one in each valve below 
the umbone, rather low and massive; crown of tooth of right 
valve excavated anteriorly and ridged posteriorly; crown of 
tooth of lett valve ridged anteriorly and sloped posteriorly. 
Umbonal ligamental fulcra, each a furrow excavated in the 
hinge-plate, between the umbone and tooth. Scars of the an- 
terior set of pedal muscles, situated above the anterior adductor 
muscular impressions. 
Anthracosia differs from Unio, to which genus the majority of 
the Unioniform shells have been referred, in its simpler dental 
system and in the absence of supplementary pedal muscles. It 
has no relation to Cardinia, in which genus others of the 
Unioniform species have been placed; whilst other members of 
genus possessing the outward appearance of certain ayiculoid 
forms of Modiola have been ranged in the genus Myalina. 
Distribution, 61 species. Devonian—Carboniferous. West- 
phalia, Saxony, Russia, Belgium, Great Britain, N. America. - 
CARBONICOLA, M‘Ooy, 1855 (see p. 470). 
Synonym, Prisconaia, Conrad, 1867. 
Example, Unio acutus, Sow. 
Cardinal tooth in right valve diverging obliquely towards the 
posterior side; lateral 1-1, long and lamellar; no lunate im- 
pression on the yentral margin of the anterior adductor as in 
Unio. 
This genus is related to Anthracosia, but differs in having 
lateral teeth. 
Distribution, about 20 species. Coal Measures. Europe, 
United States. 
* See p. 430, ¢ See p. 432 
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