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BRACHIOPODA. ota 
a broad 4-partite hinge-plate, with processes from the outer 
angles of the dental sockets; crura of the spires united by a 
transverse band supporting a small process. fossil, 2 species. 
Upper Lias, Normandy. 
ATHYRIS, M‘Coy. 
Iitymology, a, without, thuris, a door* (i.e. deltidium). 
Synonyms, Spirigera, D’Orbigny. Cleiothyris, King (not 
Phil.), 
Types, A. concentrica, Buch. A. Roissyi, Figs. 169, 170. 
A. lamellosa, Pl. XV., Fig. 16. 
Shell impunctate, transversely oval, or sub-orbicular, bi- 
conyex, smooth, or ornamented with squamose lines of growth, 
_ Sometimes developed into wing-like expansions (Fig. 170+); 
/ I 
CHET | 
Fig. 169. Interior of dorsal valve. Fig. 170. Specimen with fringe. 
hinge-line curyed, area obsolete, foramen round, truncating the 
beak, deltidium obsolete ; hinge-plate of dorsal valve with four 
muscular cayities, perforated by a small round foramen, and 
supporting a small complicated loop (?) between the spires; 
spires directed outwards, crura united by a prominent oral . 
loop. 
The foramen in the hinge- plate occupies the situation of the 
notch through which the intestine passes in the recent Rhyn- 
chonellee ; in A. concentrica a slender curved tube is sometimes 
attached to the foramen, beneath the hinge-plate. A. twmida 
has the hinge-plate merely grooved, and the byssal foramen is 
angular, 
Fossil, about 70 species. Silurian—Lias. North and South 
America and Europe. ) 
* Sometimes employed, incorrectly, in the sense of a door-way or for men. 
+ The spurious genus Actinoconchus (M‘Coy) was founded on this character; similat 
expansions are formed by species of Atrypa, Camarophoria, and Producta, 
