802 REPORTS ON THE STATE OF SCIENCE.—1913. 
Summarising, we find that there is a considerable amount of 
evidence pointing to the presence in primitive Testudinata of epithecal 
elements, lying on the thecal shell and completing it on the sides of 
the trunk. These elements were obviously arranged in a number of 
Fig. 7. Diagrammatic transverse section through the shell of a hypothetical Prochelonian. 
Elements of thecal layer dotted, of epithecal layer black. 
Cost, cost ; cost.Pl, costal bony plates ; cost.R, costal row of epithecal elements ; 
Epn, epineurals; im.R, inframarginal row ; mpl.R, median plastral row ; mrg.h, 
marginal row; nc.R, neurocostal row; Pl, plastron; pl.R, plastral row; sm.R, 
supramarginal row ; Sk, outer layers of skin. 
longitudinal rows (fig. 7). In Dermochelys there are seven dorsal and 
five ventral rows of larger dermal ossifications, the dorsal ones being 
part of the mosaic shell and forming longitudinal keels on the back 
‘ q 1 \ = Yn Sh 
\ 
i pl Sh 
PL 
1 
th. Sh 
Fig. 8. Diagrammatic transverse section through the shell of a normal thecophorous 
tortoise. Elements of thecal layer dotted, of epithecal layer (the marginals) 
shaded ; horny shields (probable representatives of epithecal elements of fig. 7) 
black, 
Cost, cost ; cost.Pl, costal bony plate; c.Sh, costal horny shield ; «h.Sh, inter- 
humeral shield (representing the median plastral row in fig. 7) ; im.Sh, inframarginal 
shield; mrg.Pl, marginal bony plate; m.Sh, marginal horny shield; n.Pl, neural 
plate ; ».Sh, neural shield; P/, plastral bony plate; pl.Sh, plastral shield; sm.Sh, 
supramarginal shield. 
(fig. 1). We have evidence of corresponding rows of epithecal elements 
in the thecophorous Testudinata (compare fig. 1 with figs. 7 and 8), 
the median dorsal row being represented by the epineurals and neural 
