134 ARTHRODIRAN LUNG-FISHES 
have permitted the head to be thrown backward to a 
degree which suggests the thoracic joint of an Elater. 
On the ventral side of the trunk there occurs a flattened 
plastron (Fig. 132): its dermal elements are connected by 
overlapping margins; they are lighter, and in some forms 
(Fig. 135) lack the tuberculate surface of the dorsal 
plates. Dorsal and ventral shields are connected by stout 
lateral elements (Fig. 132, /Z), which, passing ventrally, 
FIG. 135 
Figs. 134-13'7.— Dermal plates of Dinichthys. 134. Associated plates of head 
and shoulders. 135. Plates of ventral armouring. (After A.A. WRIGHT). 136. 
Pineal plate of Dinichthys intermedius, surface view. 137. Pineal plate of Dinich- 
thys terrelli, visceral aspect. 137A. Pineal plate, in sagittal section. 
ADL, Antero-dorso-lateral. AVL. Antero-ventro-lateral. AVM. Antero- 
ventro-median. £. Ethmoid. £O. Epiotic. MO. Median occipital. PN. 
Pineal. PO. Preorbital. P7O. Postorbital APVL. Postero-ventro-lateral. SO, 
Suborbital. .X. External aperture, and >, the axis of the pineal funnel. 
meet in the median line, and become the anterior support- 
ing rim of the plastron. By some writers these have been 
homologized as “ clavicles.” 
In further detail little is known of the anatomy of 
