BRACHIOPODA. 



233 



^he supposed Carboniferous species (Hypodema, D.K.) is, perhaps, related 

 o Pileopsis. Calceola is shaped like Cyrtia., and its hinge-area resembles 

 hat of some Strophomenas. 



FAMILY V. PRODUCTION. 



Shell concavo-convex, with a straight hinge-line; valves rarely articu- 

 ated by teeth ; closely appressed, furnished with tubular spines ; ventral 

 'alve convex; dorsal concave; internal surface dotted with conspicuous, 

 unnel-shaped punctures; dorsal valve with a prominent cardinal process; 

 irachial processes (?) sub-central; vascular markings lateral, broad and 

 imple ; adductor impressions dendritic, separated by a narrow central ridge ; 

 Central valve with a slightly notched hinge-line ; adductor scar central, near 

 he umbo ; cardinal impressions lateral, striated. 



Fig. 153. Producta gigantea, % Carl, limestone. 



A, interior of dorsal valve ; B, interior of ventral valve, with the umbo removed; 

 ), ideal section of both valves ; D, hinge-line of A ; .;', cardinal process; a, adductor; 



cardinal muscles; b, oral processes?; *, hollows occupied by the spiral arms ; v , 

 'ascular impressions ; h, hinge-area. 



