.WEALDEN CROCODILES. " 629 



In the series of five vertebrae, including the three hinder lumbars and the sacrum (ib., 

 fig. 4), the costal surface has been transferred to the diapophysial ridge, d, which now extends 

 outward from a contracted base midway between the zygapophyses, the terminal articular 

 surface being supported by a lower buttress-like ridge,/. The under surface of the 

 centrum is here broader than in the preceding vertelira, and is transversely rounded : 

 the carinate character in the dorsal vertebrae, giving space to the abdominal cavity, has 

 here disappeared. In some of the present series the deeply concave side of the centrum has 

 yielded to pressure, and the compact outer wall has been fractured and pressed in upon 

 the chondrosal or quasi medullary cavity. In the last lumbar vertebra the diapophysis, 

 depressed and subelongate, shows a narrow costal surface, d', for a small or short ' false 

 rib.' 



The two hindmost vertebrae in this series of five are sacral (.? i , « 2) . They have the 

 crocodilian character of limited number, and the non-dinosaurian character of retaining 

 their neural arch in normal junction with the centrum. The doubt expressed as to the 

 ordinal affinities of Poilcilopleuroji,* in my ' Report,' is here dispelled. The diapophysis, 

 short, but broad and deep {s 1, d), terminates in a large flattened semi-oval surface for the 

 sacral rib. The corresponding surface upon an equally large diapophysis in the second 

 sacral has rather less vertical extent(s 2, d)- The centrums appear to have coalesced, but 

 the primitive line of separation of the terminal expanded surfaces is traceable. 



The neural spines are broken aw^ay in all this series of vertebrae, but their narrow 

 elongate bases indicate the same character as in the detached more anterior vertebra 

 from a smaller individual (figs. 1 and 3, ns). 



The two caudal vertebrae (figs. .5 — 8) are from the terminal part of the tail where both 

 transverse and spinous processes have disappeared. The low neural arch has coalesced 

 with the centrum, and this, retaining its length, as in the sacral and lumbar region has 

 diminished by loss of transverse and vertical extent. The under surface is canaliculate 

 (fig. 7), and both the anterior and posterior expanded ends of the boundary ridges of the 

 lower groove have articular surfaces, h, h, for a haemal arch. 



In Plate 39, fig. 9, the compressed subtriangular portion of an abdominal sternum (?) 

 is marked hs ; the pair of abdominal ribs which articulate by expanded thinned-off 

 ends to the sides of hs are marked h, h. 



The ungual phalanx (ib., figs. 12, 13) is remarkable for its degree of curvature, its 

 strong lever-process, and the deep lateral grooves. 



The value of this little specimen and fruit of Mr. Fox's persevering researches in 

 the Wealden deposits of his vicinity is its demonstration of the limited crocodilian 

 number of trunk-vertebrae deprived of reciprocal motion upon each other, and with 

 transverse processes thickened and terminally expanded for junction with the pelvis. 



* " Subsequent discoveries may prove it to belong, like the Megalosaums, to the Binosaurian order ; 

 but, as the Poi/ciloplein-on is, at present, known, it seems to have most claim to be received into the crelor 

 spondjlian family of the Crocodilian order," ' Kep. Brit. Assoc.,' 1S41, p. 85. 



