ORDER III TELEODESMACEA 405 
depressions (Fig. 732, a, x’) next the sinus were shown by Petho to have been the seat 
of a ligmentary connection between the valves; the adductor scars (a, a’) resemble 
those of Radiolites. Widely distributed in the Middle and Upper Cretaceous. 
The supposed genera Dipilidia, Birostrites, and Jodamia are based on internal 
casts of Radiolites. The visible submersion of the ligament in some Radzolites enables 
us to understand how the stages shown by Hippurites have arisen. 
Family 14. Hippuritidae. Gray. 
Shell substance of two layers, the external porous, grooved, and punctate ; the inner 
lacunary and prismatic; exterior with sutwres corresponding to an “anal” and 
“branchial” inflection, and sometimes with a ligamentary suture ; clithrum formed of 
two processes tn the free valve, the adductors attached to myophores ; fixed valve with one 
thin laminar process ; the adductor scars excavated, the anterior adductor duplex, forming 
distinct scars. Cretaceous. 
Hippurites, Lam. (Figs. 733-737). Lower valve cylindro-conic, sometimes a metre 
in length, attached by the apex, smooth or longitudinally ribbed, with three furrows 

Fic. 735. 
Hippurites organisans, 
re 3.5 Montf. Vertical section 
Fig. 733. Fic. 734. of a valve below the 
Hippurites Gosaviensis, Hippurites Oppeli, Douvillé. Nefgraben, near Russ- living chamber, show- 
Douy. Upper Cretace- bach, Salzburg. A, B, C, Impressed lines bounding ing the septa and inter- 
ous; Gosau_ Valley, convex vertical areas (columns) corresponding to the septal cavities of the 
Austria. 1/9. region of the hinge. 1/9. middle layer. 1/}. 
bounding two “columns,” or columnar areas, extending from the apex to the upper 
margin (A, B,C). Upper valve depressed, conic, with sub-central umbo, usually with 
two round or oval foramina ; outer surface showing pores, the apertures of short canals 
which join larger canals radiating from the beak. The thick outer layer of the lower 
valve is usually brown-coloured and made up of thin horizontal strata, which are in 
turn composed of small vertical prisms. The white inner layer is porcellanous, and 
sometimes contains vacant spaces in the lower part of the shell. Three prominent 
folds are present, on the inner side of the shell, formed by the inbending of both 
layers of shell, and corresponding to the external grooves (A, B, C). Of these the 

