ASTEROLEPIS MAXIMA. 81 



reminds us in its shape of the conventional " spade" on playing cards. Above, it 

 is carinated like the hinder part of the plate in front, but shows no arti- 

 cular surface whatever. Its broad free posterior aspect terminates the upper 

 part of the carapace behind, and forms a conspicuous backwardly directed, 

 pointed projection ; the longer lateral margins slope gently inwards as well as 

 forwards, joining at obtuse angles the short straight antero-lateral ones, which, 

 uniting in front, form the sharply pointed apex of the plate. On the under aspect 

 (woodcut, Fig. 41) a conspicuous rounded ridge connects the postero-external angles 

 across the base of the posterior pointed process, in front of which three marginal 

 articular surfaces are seen. Two of these (d. and e.) lie along the lateral margins, 

 one on each side, and overlap the posterior dorso-lateral plates ; while the 

 third (/.), anterior and median, lies just at the apex, where it forms a broad-based 

 isosceles triangle, which fits over the corresponding area noticed at the posterior 

 extremity of the superficial aspect of the anterior median dorsal. 



The anterior dorso-lateral (PL XVI, fig. 3 ; and woodcuts, Figs. 42 and 43) is 

 oblong-pentagonal, and shows five margins, — an anterior, a superior, an inferior, a 

 postero-superior, and a postero-inferior. Of these five the anterior is oblique 



Fig. 42. Fig. 43. 



Fig. 42. — Restored sketch of superficial aspect of right anterior dorso-lateral plate. /., articular surface 

 alon<* the upper margin for the anterior median dorsal ; g., surface along the lower margin for the anterior 

 ventro-lateral ; h., processes for articulation with the external occipital ; n., lateral line groove. 



Fig. 43. — Deep surface of right anterior ventro-lateral plate, z., surface for articulation with the 

 posterior dorso-lateral plate. 



when the plate is looked at detached from the body, and forms an acute angle 

 with the upper and an obtuse one with the lower margins ; the upper and lower, 

 of which the upper is the longer, are nearly straight, or only slightly convex ; 

 while the considerably shorter postero-superior and postero-inferior margins meet 

 each other in a backwardly directed angle, which is nearly a right one. On the 

 superficial aspect two elongated articular area? are seen, one (/.) along the upper 

 margin, over which the anterior part of the outer edge of the anterior median 

 dorsal fits ; the other (g.) lies along the inferior margin, and is overlapped by the 

 anterior ventro-lateral ; lastly, traversing the surface of the plate from before 

 backwards at the junction of its lower and middle thirds, is the lateral sensory 

 groove (n.). 



Turning now to the concave inner surface of the plate, we find posteriorly a 



