334 MR. W. K. PARKER ON THE OSTEOLOGY OF BALZNICEPS REX. 
was one of these free hemapophyses on the right side with the rudiment of a second 
near its tip; whilst on the left side there were two such bones, the anterior piece 
being very long, passing downwards more than an inch behind its homotype of the 
pelvic rib, and upwards of an inch behind the rib itself. A structure this well worth 
noticing, bringing us, as it does, so near to the condition of these parts in the Crocodile. 
In the Puffin (Fratercula arctica), and in the genera Alca and Uria the posterior ribs 
and hemapophyses are prolonged so far backwards that the very angular articulation 
of the last or pelvic nearly reaches as far back as the tip of the very long and slender 
os pubis. 
Sacral and Caudal Vertebre. (Pl. LXVL. fig. 1 sc, cd; & Pl. LXVII. figs. 2 & 3 sc, & cd.) 
The first two sacral vertebree are almost as large as the dorsals, and their boundaries 
are very distinct ; they then rapidly decrease in size and in distinctness ; yet the next 
four are indicated by their short blunt pleurapophyses, the last two of which scarcely 
reach the ilium. The stunted pleurapophysis of the right side of the second sacral is 
not anchylosed to its parapophysis. After the first six, the next five sacrals have their 
extremely small pleurapophyses confluent with the sides of the centrums, without any 
out-standing part. The remaining six sacrals have out-standing coalesced pleurapo- 
physes, the second and third of which are extremely thin, and are principally composed 
of threads of diploe. The neurapophyses of all the sacrals except the last have in this bird 
completely coalesced. Between the first and second sacral there is a large oval foramen 
for the exit of nerves, but it is much less than the passage formed in the dorsals between 
the neurapophyses of contiguous vertebra. The posterior and anterior roots of the 
spinal nerves have separate outlets in the rest of the sacrum ; and from these passages 
to the roof of the pelvis there is a large quantity of very rich diploe involving the sub- 
stance of the neurapophyses, neural spines, diapophyses, and pleurapophyses. The 
neural spines of the sacrum are at first equal to those of the dorsals, but between the 
acetabula they spread, become rounded, and then obsolete. There is in this, as in 
most birds, a large triangular space for the insertion of the dorsal muscles on each 
side the sacral spines ; the roof of this space is oblique and is formed by the ilium ; the 
floor is horizontal, and consists of the diapophyses. 
Looking at the pelvis from above (Pl. LXVII. fig. 2), there may be seen two pairs of 
small passages between the spine and the iliac bones, just as these large bones begin to 
divaricate before they turn outward on each side towards the acetabula. Behind these, as 
the spine gains breadth but loses height, there is a deep fissure divided by oblique septa on 
each side of the spine ; these septa are the diapophyses of the middle part of the sacrum. 
The iliac bones become further and further apart ; and where they join the coalesced 
dia- and neur-apophyses, four pairs more of oval passages, most of them quite small, 
indicate from above the boundaries of four more of the sacral vertebree. Two additional 
pairs of large transversely oval openings or interspaces, the anterior pair of which is 
