BRACHIOPODA 177 
body, and may be coiled in a very complicated manner. In 
Rhynchonella the lophophore is 
protrusible, but this is excep- 
tional. 
The edges of the mantle 
usually carry a row of setae, 
which arise from ectodermal pits, 
as in Chaetopods. 
The intestine in Lingula is of 
some length, it takes one or two 
twists, and terminates in an anus 
which opens at the right side into 
the mantle cavity between the 
shells. In Discina also the anus 
is lateral, but in Crania it opens 
in the median line into a cavity 
which lies between the posterior 
ends of the valves where the 
peduncle would normally be 
found. 
The food of Brachiopods con- 
sists chiefly of Diatoms and 
minute unicellular Algze, which 
are brought to the mouth by the 
action of the cilia on the lopho- 
phore. 
The only case of serial repeti- 
tion of parts presented by the 
Brachiopoda is the two pairs of 
nephridia found in the genus 
Rhynchonella. 
The sexes are separate in 
Crania, but Lingula, and probably 
some others, are hermaphrodite. 
The recent Brachiopods are 
found in all seas, usually at 
moderate depths, within 100 
fathoms. Lingula and Gilottidia 
ODMH OR oot 
oie’ 
Ho 
tH 
3) 
= 
. 113.—Lingula anatina.  Dia- . 
gram showing the muscular 
system: after Hancock. 
. Dorsal valve. 
. Ventral valve. 
Peduncele. 
Heart. 
Alimentary canal. 
Anal aperture. 
Umbonal muscle. 
Central muscle. 
. Transmedial muscle or sliding 
muscle. 
. Anterior muscle. 
. Middle muscle. 
. Adjustors, enabling valves to 
move forward and backward on 
each other. 
sometimes live between tide marks, but may extend to a 
12 
