132 M0LLU8CA. 



No, 401. Productus horridus, Gein. 



The members of this genus were mostly free when adult. The shell is 

 auriculate, large beaked, and with linear indistinct hinge-line; no hinge teeth; 

 81 species. Permian, Gera, Saxony. 



No. 403. Productus longispinus, Sow. 

 Carboniferous, near Peru, 111. 



No. 403. Productus Prattenianus, Norwood. 

 Coal Measures, Knox Co. , 111. 



No. 404. Productus semireticulatus, Mart. 



Carboniferous Limestone, Longniddy, near Edinburgh, 

 Scotland. 



ORDER LYOPOMATA. 



Valves not united along a hinge-line; mantle lobes free; intestine with an 

 anal aperture. 



FAMILY CRANID-ffi. 



Shell orbicular; no hinge, dorsal valve limpet-shaped. Animal attached to 

 objects by the ventral valve. 



No. 405. Crania scabiosa, Hall, 



Dating from the Lower Silurian, with 37 fossil species; the group is still 

 living. Cincinnati Group, Cincinnati, Ohio. 



FAMILY DISCINID^. 



Animal attached by peduncle passing through the ventral valve; arms 

 fleshy. Ranging from the Silurian to the present time. 



No. 406. Discina nitida, Phil. 



Upper valve limpet-shaped; lower or ventral valve fiat or conical ; 64 fossil 

 and 10 living species, ranging from the Silurian age. Coal Measures, Spring- 

 field, 111. 



