BRACHIOPODA. 
_ beak to.the anterior part of the valve. Dorsal valve depressed 
without an area, and with a distinct mesial fold. Shell-structure 
punctate. 
Fossil, 2 species. Carboniferous. United States, Ireland, 
Belgium. 
CyrtTinA, Davidson, 1858. 
Etymology, modified from the diminutive (Cyrtidiwm) of 
Cyrtia. 
Examples, C. heteroclyta, C. Demar- a. 
lu, and C. septosa. ‘ 
Shellresembling Spirifera, but with- 
out the vertical shelly plates which 
diverge from the extremity of the beak. 
Interior of ventral valve with two con- 
tiguous vertical septa, which coalesce 
into one median plate, which extends 
from the extremity of the beak to within 
a short distance of the frontal margin, = 
and then diverges to form dental plates, _ | Fig 20. 
as in Pentamerus. ‘The fissure is co- . ee oa Doetal hee a 
vered by an arch-shaped deltidium ; 4eltidium ; 2, v-shaped chamber. 
but in C. Demarlii the median septum is continued as far as 
the under surface of the deltidium, and the dental plates are 
fixed to the sides, instead of the upper edge, as in C. heteroclyta 
and C. septosa. 
‘< Spiral coils haying the same position asin Spirifera, but 
the two first coils are connected a little in front of the mid- 
length by an apparatus somewhat like that of Spirigera, but 
not so complicated. A very slender process springs upwards 
towards the ventral valve from each coil, and, at a height of 
about one line, curves forwards. The two then unite and forri 
a single band, which extends forwards to about the front of tha 
coil, and there ends in an obtuse point.” —(Billings. ) 
Distribution, 9 species. Devonian—Trias. Europe and 
North America. 
~~ 
UN 
LLP 
& 
MERISTELLA, Hall, 1860. 
Etymology, diminutive of Merista, an allied genus. 
Examples, Atrypa tumida, Dal. ; Meristella levis, Hall. 
Shell oval, ovoid, orbicular or transverse. Valves unequally 
conyex, with or without a median fold and sinus; beak appa- 
rently imperforate, incuryed; area none. Surface smooth or 
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