THE FORE FEET. HI 



The distal end (figure 6) presents a semi-oval articular face, not 

 extending quite to the anterior part of the bone, and supporting in life the 

 well developed, sliort, first metacarpal. This articular face is somewhat 

 saddle-shaped, being convex along its short diameter, and slightly concave 

 lengthwise. 



The main dimensions of the trapezial bone in two specimen* of the 

 Diiiocerata are given below. 



Measurements of Left Trapezium. {Dhtoceras ndrahile, No. 1208.) 



m. 



Length of longitudinal axis of trapezium, .._.... .036 



Greatest horizontal diameter, _ .062 



Least horizontal diameter, ......_ .03fi 



Longest diameter of proximal articular face, 04 4 



Transverse diameter of proximal articular face, .026 



Longest diameter of distal articular face, __ .048 



Transverse diameter of distal articular face, .026 



Measurements of Right Tra2}€ziuu). {Tinoceras lngens,Tso. 1219.) 



m. 



Length of longitudinal axis of trapezium, 03 7 



Greatest horizontal diameter, .068 



Least horizontal diameter, _ _ .031 



Greatest diameter of proximal articular face (approximate), . .045 



Transverse diameter of proximal articular face, ... .032 



Greatest diameter of distal articular face, ...__. .0.')3 



Transverse diameter of distal articular face, 030 



The Trapezoid. 



(Plate XXXTII, figures 7-12, Plate LIV, figure 1, tr ; 

 and woodcuts 110-120, below.) 



The trapezoid is a small bone in tlie Dhiorerata, being- much the 

 smallest (if the carpals, with the exception of the pisiform, and perhaps 

 also of llie central, if separate. The general shape of the bone is that of 

 a blunt, nearly square, wedge, the large end being presented to the 

 suj)erior, or anterior, surface of the foot. 



Tliis end of the bone is represented in Plate XXXIII, figure 7, and 

 shoMS nearly all that can~l)e seen of it when in its natural position with 



