﻿KIMMERIDGE CLAY. 



61 



The anconal surface (PI. XVIII, fig. 1) of the shaft is almost fiat and lies more on the 

 plane of that surface of the entire metacarpus than in the marginal metacarpal above 

 described (fig. 3). The radial and ulnar surfaces of fig. 1 converge palmadtothe narrow 

 convex palmar surface which forms the rounded angle of the proximal triangular tract 

 (ib., fig. 6, ur,p). Both radial and ulnar surfaces of the shaft are concave lengthwise and 

 across (ib., fig. 2, r). The transverse concavity of the distal articular surface is 

 feebly indicated, and the bifid character of the joint is scarcely marked, though fractured 

 surfaces suggest that a pair of low palmar prominences may have been broken away ; 

 but the joint is much less trochlear than in the first metacarpal (ib., fig. 6). 



A metacarpal of similar type to the preceding has suffered too great mutilation of 

 both ends to serve for profitable description ; it is not a corresponding metacarpal of the 

 right fore-foot, but may be either a second or third, though from the slight superiority of 

 length I should judge it to have been the second metacarpal of the same left fore-foot as 

 the subjects of PI. XVIII belonged to. 



A metacarpal with a subtriedral shaft, and an oblique twist at its basal half through 

 an extension radiad of the radial angle, upon which angle the flat proximal articular 

 surface has extended for the metacarpal on that side, is evidently a fifth metacarpal bone. 

 The distal surface (PI. XIV, fig. 6) is oblong and almost flat save where it becomes convex 

 on being continued from the basal upon the radial surface ; it is feebly concave trans- 

 versely at its middle half, but this is not continued, deepening, so as to divide the palmar 

 part of the joint into a pair of trochlear condyles. The length of this metacarpal is 

 5 inches 9 lines ; the breadth of the proximal end is 4 inches ; of the distal end 3 inches 

 2 lines ; the breadth of the middle of the shaft is 2 inches 3 lines. 



The largest of the proximal phalanges extracted gives a length of 5 inches 5 lines ; 

 with a breadth of the proximal end of 4 inches, and a breadth of the distal end of 3 inches 

 7 lines. The breadth of the middle of the shaft is 3 inches ; and this seems not to have 

 been more than 1 inch 7 lines in ancono-thenal diameter, but the thenal surface is 

 partially crushed in. The anconal surface is smooth and flat save toward the expanded 

 articular ends. The proximal surface, moderately concave, appears to have been adapted 

 to a distal articular surface of the simple character of the metacarpal last described (PI. XIV, 

 fig. 6). The distal surface of the phalanx is moderately trochlear, i. e., with a feeble 

 transverse concavity along its middle half; it is strongly convex throughout in the opposite 

 (anconothenal) direction. The size of this proximal phalanx indicates it to have belonged 

 to one of the larger middle digits. 



Of the instructive terminal phalanges, the most entire forms the subject of figs. 4 

 and 5 of PI. XV. The small proportion of the thin, smooth, punctate, articular surface 

 shows a partial depression at b, fig. 4 ; but the bone is so slightly abraded where that thin 

 smooth crust is wanting as to afford a fairly true figure of its general shape, which is 

 almost flat, with a feeble sinuosity. The anconal border {a) is most produced ; conse- 

 quently that surface of the phalanx is longest ; but it is little more than half as long as it 



