DR. A. GUNTHER'S DESCRIPTION OF CERATODUS. 
539 
The venous trunks, by which the blood is carried to the atrium of the heart, have been 
mentioned above. The two anterior venue cavce collect the blood from the head and 
fore limbs, and offer no further peculiarity. The course of the vena pulmonalis is noticed 
with the organ to which it belongs. The single vena cava posterior (Plate XL. x, and 
Plate XLI. e) is the largest vessel in the whole system, having a diameter of 3 lines, 
and collecting the blood from the trunk, tail, and the abdominal organs, except the 
lung and intestine. Immediately below the diaphragm it enters the liver, collecting 
the blood from this organ, and descends through the substance of the right lobe of the 
liver (Plate XXXIX. x ) to and along the inner margin of the testicle (or ovary) of the 
same side, being rather superficial whilst it accompanies this organ. It receives in suc- 
cession from the front towards behind the following branches : — 
a. A number of very small branches from the right testicle (or ovary) which join 
the main trunk at right angles. 
b. A stronger branch from the hindmost lobe of the right testicle and upper part of 
right kidney (Plate XLI. g). 
c. A very strong vein from the left testicle (Plate XLI. jf), which corresponds in 
situation and function to the main trunk, and might be called a left vena cava posterior ; 
but the currents of blood in the two run in opposite directions, that of the right (main) 
trunk running towards the head, that of the left towards the tail. 
d. The vena caudalis (Plate XLI. h) is the strongest tributary ; it enters the main 
trunk on its dorsal surface, immediately after having penetrated through the muscles 
and fascia which cover at this place the vertebral column. 
e and f. A pair of venae renales revehentes (Plate XLI. fig. 1, i i). 
The Gills (Plate XXXVII.). 
The gill-apparatus differs considerably from that of Lejgido siren, and approaches in 
structure that of the common Teleosteous type. Of the five branchial arches, four bear 
complete gills (figs. 8 & 9). Each gill is a broad membranous fold, to which a series of 
numerous simple branchial laminae is attached in front and behind ; most of the laminae 
extend somewhat beyond the connecting membrane, having their extremities projecting 
free beyond its edge. The outer point of attachment of the gills is not on the branchial 
arches, but beyond them, on the wall of the gill-cavity (u, u) — the three anterior being- 
fixed to the lower surface of the lateral expansion of the skull, and the fourth to the 
inner surface of the suprascapula. The fifth pair of arches (w) (commonly called “ lower 
pharyngeals ”) retain in our fish their primitive function, and, although not bearing a 
perfect gill, are, at least, provided with gill-rakers. Two series of short, closely set gill- 
rakers, closely interlocking with those of the neighbouring arch, run along the concave 
side of each of the four principal arches. 
Further, to this gill-apparatus is added a very distinct pseudobranchia ( x ). This 
pseudobranchia is the gill originally belonging to that branchial arch which is modified 
into the hyoid. It is also accompanied by two series of gill-rakers, one of which (x 1 ) 
