THE NORTHERN RIBBON-FISH. 13 
The Vertebral Column (Pl. IL, Fig. 10). 
The vertebral column consists of 101 slender and excessively fragile vertebree, 
eight more, that is to say, than are present, according to ParKER, in Regalecus 
argenteus. The vertebree agree in general with, but differ in points of detail from, 
those of that genus. Each centrum is deeply amphiccelus, consisting as it were of 
two delicate cones, placed apex to apex, where in most cases a small aperture places 
the invertebral substance of the two sides in communication. The outer surface of 
the centrum presents a series of parallel radiating lamelle, arranged like the slats of 
a water-wheel, and binding the two cones together. On the dorsal aspect of the 
centrum two somewhat similar but modified lamelle arise. Each of these is 
elevated anteriorly and posteriorly into a pointed triangular zygapophysis, while 
between these arises a more delicate newral process, which meets its fellow of the 
other side to form a neural arch, from which arises the long slender neural spine. 
The neural process is usually approximated to the anterior zygapophysis : and 
the two anterior zygapophyses are usually somewhat near together, and fit in between 
the posterior zygapophyses of the preceding vertebra. 
From the under side of the centrum two haemal or transverse processes project 
downwards, enclosing between them one, two, or more lamelle. Each haemal 
process is expanded at the base, especially on its anterior aspect, and each is 
strengthened by a ridge on its outer surface which is paralleled by a similar but 
weaker ridge at the base of the neural arch and spine. The first forty-three haemal _ 
processes are free, but the remaining ones unite to form haemal arches and haemal 
spines, which are not present in any part of the body of Regalecus. 
PaRKER calls attention to the remarkable increase in length of the vertebral 
centra in Regalecus, from the anterior to the posterior end of the series. A similar 
increase is traceable in Trachypterus, but only as far as the ninety-second vertebra, 
beyond which the centra diminish again; and the vertebree nowhere exhibit such 
an extraordinary length of centrum as Regalecus displays in the posterior half or 
third of its body. 
Fig. 5. ANTERIOR ASPECT OF ATLAS, DORSAL AND CAUDAL VERTEBRA. 
(The neural spines of the two latter are broken off.) 
In Trachypterus the first centrum is a thin curved disc ; that of the second is 
