BiucnroroBA. 383 



witli diyerglng branches; cardinal and adductor impressions 

 distinct. Tlie furrowed cones undoubtedly indicate the existence 

 of spiral arms, similar to those oi Atrypa (Fig. 180), but desti- 

 tute of calcified supports. The ujDper valve sometimes exhibits 

 markings derived from the surface on which the shell has grown. 

 The mantle-lobes seem to have continued depositing shell 

 until the internal cavity was reduced to the smallest possible 

 limit. 



Fossil, 3 species. Devonian — Trias. '^ 



Ventral valve. 



Calceola, Lamarck. 



Etymology, calceola, a slipper. 



Type, C. sandalina, PL XV., Fig. 2G. Fig. 188. 



Slidl thick, triangular ; valves plain, not articulated ; ventral 

 valve joyramidal ; area large, flat, triangular, with an obscure 

 central line ; hinge-line straight, crenulated, dorsal valve flat, 

 semicii'cular, with a narrow area (A), a small cardinal process 

 {j), and two lateral groups of small apophysary (?) ridges {h) ; 

 internal surface punctate-striate. 



Fossil, Devonian, Eifel, Britain. 



The supposed Carboniferous species [Hypoclema, D.K.) is, per- 

 haps, related to Pileopsis. Calceola is shaped like Cyrtia, and 

 its hinge-area resembles that of some Strophomenas. 



Family V. — Productid.e. 



Shell concavo-convex, with a straight hinge-line ; vah'cs 

 rarely articulated by teeth; closely appressed, furnished with 

 tubular spines ; ventral valve convex ; dorsal concave ; internal 

 Buiface dotted with conspicuous, funnel-shaped punctures ; 

 dorsal valve with a prominent cardinal process ; brachial pro- 

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

 simple ; adductor impressions dendritic, sejDarated by a narrow 

 central ridge ; ventral yalve with a slightly notched hinge -lir.e ; 



