1014 
SCANDINAVIAN FISHES. 
include within their cloven base the margin of the 
hypural bones and urostyle. The spinal canal extends 
straight back towards the end of the last vertebra ( t ), 
the body of which is compressed to form the urostyle 
(r), also directed straight backwards. The first (posterior) 
hypural bone (h) is really composed, in analogy to the 
primordial confluence of the last two vertebrae, of two 
haemal parts, which have been united in an arch at the 
base (proximally), just below the last vertebra, and have 
closely applied their outer (distal) extremities to each 
B 
other, thus including an elliptical cavity, in which the 
pulsating lymph-heart of the Eels is situated". The 
lower (anterior) hypural bone (between p and r) an- 
swers to the haemal spine of the penultimate vertebra, 
which also supports the hindmost haemal arch (p). In 
young Eels, as well as in the Conger, Robin found this 
hypural bone to be fairly well developed 6 and originally 
divided by a suture from the haemal arch. In older 
Eels (fig. 267, B) it is extremely narrow, and lies, in 
the form of an osseous rod, close to the under margin 
Fig. 268. Skull of an Anguilla vulgaris. 3 / 2 times the natural size. A: with branchial apparatus, jaw-bones, and orbit. B: cranium, seen 
from above. C: the same, from the right; D: the same, from below; E: the same, from behind. 
alsp, alisphenoid; bo , basilar part of the occipital; et, etv, and v, ethmoid (et) and vomer (v), confluent in front; fr, frontal; hm , hyomandi- 
bular; iop , interoperculum; /, lingual; lo , lateral parts of the occipital; mdb, mandible; mt, mastoid part of the temporal; op, operculum; par , 
parietal; pob, preorbital; pop , preoperculum; psp, parasphenoid ; ptr , petrosal; qu, quadrate; Ii. br., branchiostegal rays; so, squamosal part of 
the occipital; sob, hindmost part of the suborbital ring; sop, suboperculum; spet, supraethmoidal ; splio, postfrontal (sphenotic); squ, squamosal 
part of the temporal; uh, urohyoid. 
a In the Conger the upper (posterior) part of this hypural bone coalesces with the lower edge of the urostyle. See Robin, Journ. 
Anat., Phys. 1880, pi. XXV, figs. 1 and 2. 
b Cf. Robin, 1. c., pi. XXV, fig. 3 and pi. XXIV, fig. 4. 
