MOLLUSCOIDEA — BRACHIOPODS l8l 



Sub-class 2, Endoprocta 



Colonial or solitary Bryozoa with both mouth and anus 

 within the tentacle-bearing lophophore (whence the name from 

 Greek endon, within, + proktos, the anus). The introvert is 

 but slightly developed or absent. All forms belonging to this 

 small sub-class are marine except the American fresh-water 

 genus Urnatella. Not known in the fossil state. 



CLASS B, PHORONIDA 



Marine, worm-like, inclosed in a membranous or leathery 

 tube but unable to withdraw the soft parts of body into it ; 

 a tentacle-bearing lophophore present, very similar to some 

 bryozoan Ectoprocta. Name from Greek Fhoronis, the only 

 living genus. Not known in the fossil state. 



CLASS C, BRACHIOPODA (BRACHIOPODS) 



Type of class. — Terebraiulina septentrionalis (living) (Figs. 



73 «. ^)- 



This species is abundant off the coast of Maine, living from 

 low tide to a depth of 300 feet. It occurs from Massachusetts 

 to Nova Scotia inclusive. (Species of the same genus occur 

 in the shallower waters of nearly all seas.) 



The animal is protected by a calcareous shell, usually five- 

 eighths of an inch long and consisting of two pieces {valves). 

 It is attached to a rock or other support by a posterior, fleshy 

 prolongation of the body, called the pedicle. 



Skeleton. — The valves are secreted by two fleshy folds of 

 the body, the mantles. The pedicle passes out through a 

 hole (the pedicle opening or delthyrium) in the beak of the 

 larger or ventral valve ; hence this valve is at times called the 

 pedicle valve. Fastened to the inside of the smaller or dorsal 

 valve is a calcareous ribbon-like loop, the brachidium, form- 

 ing an internal support for the hollow, arm-like branches 



