MUSEUM OF COMPARATIVE ZOOLOGY. 13 
section shows so much uniformity of appearance that it is only by means 
of the hypophyses, or external marks, that the segments can be detected 
(fig. 2). In the neural canal (nc) and between the interneurals (cz) 
the segments are tolerably distinct. With the exception of a small lump 
in the mouth of the nerve aperture (fig. 5), there is no evidence of cal- 
cification in the vertebrze of more than half of the total. Both neurapo- 
physes and interneurals are perforated for the nerves. The interneurals 
are rather thick and strong. Small wedge-shaped interspinous pro- 
gesses (7s) extend about half-way through the crest. The ridge formed 
by the interneurals and the interspinous processes is surmounted by a 
very strong elastic cord of fibrous tissue. Over the abdominal cavity 
the hemal processes bear short flexible unsegmented ribs, and be- 
tween the hemapophyses are the small triangular interhemals (ch). 
Above the anterior portion of the anal fin the hemapophyses begin to 
take on a downward extension, gradually becoming blade-like, and over 
the posterior portion of the same fin they are supplemented by small 
pieces of cartilage (Pl. XIII. c-c), which farther back become the ra- 
dials of the caudal. The radials of the upper part of the caudal begin 
independently, or separate from the vertebrae; farther back they join 
the latter and continue to the end as if part of the column. The lines 
of separation between the vertebre and accessory cartilages are very 
indistinct ; in places, it is only with difficulty they can be traced. The 
column ends abruptly ; the terminal segment resembles a slice taken 
from the front of a following vertebra. The canals are visible at the 
end, but seem to be stopped by soft cartilage. 
The anterior vertebre of a large Heptabranchias at hand differ from 
the anterior of those described above in having the notochord segmented 
by thick membranous septa, each of which has a very small central 
perforation. Towards the tail there are vertebral constrictions, and the 
column tapers to a point. 
The Pectoral Cartilages. 
Plate XI. 
Coraco-scapulars, fig. 2.— These are strong, moderately slender, and 
taper to a point at each end. The coracoid is irregularly triangular, 
flattened below, broadened backward, and in the anterior third of its 
length — which is turned upward, like the runner of a sled, toward the 
hinder basibranchial — tapers to a point. The bent portions are an inch 
in length and nearly straight on their lower faces. They are applied to 
