VIII SIEIUIEAC, 219 
The remaining anterior skull elements are principally skeletal 
supports for the roof and walls of the buccal funnel. The roof 
is supported by an extended anterior dorsal cartilage, which is 
overlapped behind by the ethmoid cartilage, while the circular 
margin of the funnel is strengthened by a large ring-like annular 
cartilage. On each side of the latter there is a slender, rod-lke, 
styloid cartilage, and above the latter a small anterior lateral 
cartilage. All these cartilages are usually termed labial cartilages, 
and it is at least possible that they possess representatives in the 
similarly named structures of the Dog-Fish and the larvae of 
some of the tailless Amphibia. It must not be forgotten, how- 
ever, that the annular cartilage bears some resemblance to the 
ring of cartilage which encircles the lips of the buccal cavity in 
Amphioxus. 
The complex supporting skeleton of the gill-sacs forms a basket- 
like structure. It consists on each side of nine unsegmented, 
irregularly curved, and slightly branched cartilaginous rods, 
situated in the outer margins of the inter-branchial septa, 
directly internal to the skin. The first lies directly behind the 
styloid process (hyoid arch), the second and third in front of and 
behind the first gill-sac, and of the remainder one lies just behind 
each of the six succeeding gill-openings; above and below each 
gill-aperture the rods are connected by longitudinal bars, and also 
in the median ventral line by a pair of similar partially united 
bars. The dorsal ends of the rods are also connected on each side 
by another longitudinal bar, which runs alongside the notochord 
and in front blends with the chondrocranium. The rods forming 
the last pair are continuous with a cup-like cartilage, supporting 
the lateral and hinder walls of the pericardium. 
This singular branchial basket undoubtedly bears a superficial 
resemblance to the branchial arches of Fishes, but in any comparison 
of the two structures it is well to bear in mind that the branchial 
rods of the Lamprey are situated along the outer edges of the 
inter-branchial septa, and are therefore external to the gill-sacs 
and branchial arteries, and further, that they are developed in 
the somatic mesoblast of the embryonic protovertebrae, whereas 
true branchial arches are situated at the inner margins of the 
septa, internal to the gill-clefts and branchial arteries, and have 
their origin from the splanchnic layer of the mesoblast. So far 
as their position is concerned, the rods agree rather with the 
