112 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [YolXJ, 



cavity occurs on the ulnar side, but is there divided by a ridge, sloping 

 downward into two shallow depressions. This little bone somewhat re- 

 minds one of a cleaver, with the end of its handle attached to the meta- 

 cariDus. It supports at its distal extremity the second phalanx of this digit, 

 a bone having very much the same appearance and shape as the index 

 digit, only being longer and more pointed. The proximal ends of all the 

 phalangeal segments are more or less expanded, in order to su^jport the 

 ample facets of articulation that occur among them, and the metacarpus. 

 The third metacarpal is expanded transversely above, slender belaw, where 

 it falls a little beyond the medius after its confluence with it. It also 

 has a small, pointed phalanx, freely attached to its distal extremity, and 

 lying in that recess formed by the shaft and posterior expansion of the 

 first phalanx of the second digit. At a very early date, comparatively, 

 in the life of this Owl, ossification is normally extended to many of the 

 tendons of important muscles of the antibrachium and pinion. 



Of the ])elvic limb. — The lower extremity is composed of twenty dis- 

 tinct segments, including the patella, or just double the number found 

 in the pectoral limb. This increase will not surprise us when we recol- 

 lect the greater number of small bones devoted to the foot above those 

 found in the hand. Its most striking feature, next to those osteological 

 characteristics common to the family, is its extreme length, due i>rinci- 

 pally to the tibia and tarso-metatarsus. All the bones of the lower 

 limb in this species are non-pneumatic. The femur is comi)aratively of 

 good size and strong; articulated in the usual manner, it measures 4 

 centimetres in length and 7 millimetres across the condyles at their 

 widest part. At the proximal extremity, externally, above the shaft, 

 there is a flat and roughened siu'face, bounded above by the curved 

 trochanterian ridge. This surface forms the major part of the great 

 trochanter. There is no trochanter minor present. The trochanterian 

 ridge is the highest part of the bone, when it is held vertically ; it lies 

 in the antero -posterior plane, with the femur in its natural position, the 

 bird standing erect; from it, sloping directly inwards and occupying the 

 remainder of the summit between it and the head, is a smooth articu- 

 lar facet, broadest externally, merging into the globular head internally. 

 With the head it constitutes the articular surface for the pelvis — it be- 

 ing opposed to the antitrochanterian facet of the ilium, while the caput 

 femoris plays in the cotyloid ring. The excavation for the ligamentum 

 teres on the latter is conical and deep, consuming a good part of the 

 bone ; it is situated on its upper and inner aspect. In looking into the 

 relation existing among head, neck, and shaft of the femur of this bird, 

 we must observe that if the straight line lying in the middle of the 

 surface of the internal aspect of the shaft were produced upwards, it 

 would pass through the centre of the facet at the summit — if anything, 

 nearer the trochanterian ridge than it does to the head. This facet also 

 is notably narrower just before arriving at the head than at any other 

 point. Again, the plane passing through the external and circular bound- 



