16 THE VOYAGE OF H.M.S. CHALLENGER. 



trapezium articulated with 1st and 2nd metacarpals, trapezoid, and scapholunar. The 

 trapezoid articulated with the trapezium, 2nd metacarpal, scapholunar, and os magnum. 

 The os magnum, was one of the smallest bones of the carpus, and articulated with the 2nd, 

 3rd, and 4th metacarpals, the trapezoid, scapholunar, and cuneiform. The unciform was 

 shut out from the inner border of the wrist by the approximation and articulation of the 

 5th metacarpal with the cuneiform ; it articulated with the 4th and 5th metacarpals, the os 

 magnum, scapholunar, and cuneiform. The carpal bones were roughened on their palmar 

 and dorsal surfaces for the attachment of ligaments, but there was an absence of the 

 ridges and processes which characterise the corresponding bones in the human carpus. 



The digits were five in number, and both the entire digit and its metacarpal segment 

 diminished in length from the pollex to the minimus. The three segments of the pollex 

 were longer than the corresponding segments in any of the fingers. The so-called 

 metacarpal of the thumb and the phalanges generally possessed three centres of ossifica- 

 tion, one for the shaft and one each for a proximal and a distal epiphysis ; the ungual 

 phalanx, however, had only a proximal epiphysis. The metacarpals of the four fingers 

 had only a distal epiphysis, and if a proximal epiphysis had ever been present, it had 

 become fused with and indistinguishable from the shaft of the bone. The 1st metacarpal 

 articulated with the trapezium ; the 2nd with the trapezium, trapezoid, os magnum, and 

 3rd metacarpal ; the 3rd with the os magnum and 2nd and 4th metacarpals ; the 4th 

 with the os magnum, cuneiform, and 3rd and 5th metacarpals ; the 5th with the 

 cuneiform, unciform, and 4th metacarpal. 



Pelvis. — The pelvis consisted of the sacrum and two innominate bones. The sacrum 

 has been described above. Each os innominatum articulated by the inner or sacro-pelvic 

 surface of the ilium with the area on the 1st sacral vertebra, which was partly auricular 

 and cartilaginous, and partly rough for the great sacro-iliac ligament. In the larger 

 animal, a male, the length of the bone was 320 mm., in a smaller specimen, a female (c), 

 215 mm. The acetabulum, though relatively deep, had only a feeble brim, and the non- 

 cartilaginous covered surface at the bottom was narrow and grooved. The ilium was 

 short, 98 mm., and its crest was 135 mm. long. Its dorsal surface was more than 

 twice as broad as the ventral surface. From the sacro-iliac joint the bone inclined almost 

 transversely outwards to the iliac crest, which was only a little anterior to the transverse 

 plane of the base of the sacrum. The os pubis, ischium, and obturator foramen were all 

 elongated, as is characteristic of the seals, and the diameter from the pectineal tubercle 

 to the pubic symphysis was 240 mm. The junction of the os pubis and ilium was 

 marked by a large pectineal tubercle for the insertion of the psoas parvus. In the larger 

 of the two pelves measured the ischium and os pubis were not fused with each 

 other at the pubic symphysis, but in the smaller female specimen the fusion was com- 

 plete. The ischial tuberosity was moderate. The epiphysial cartilages at the symphysial 

 end of both pubis and ischium, at the iliac crest, the ischial tuberosity, and the pectineal 



