ON THE GENERAL MORPHOLOGY OF THE MYXINOID FISHES. 763 
few nests of hard cartilage. It soon fuses below with the dorsal extremity of the first 
branchial arch, and then passes downwards and backwards over the roof and on to the 
lateral wall of the pharynx under the constrictor muscle to subsequently fuse below with 
the upper end of the second branchial arch. It is continued beyond the latter arch as 
a small rod, rising slightly until it again reaches the roof of the pharynx, where it 
terminates sometimes in a bifid extremity. This, however, may vary in the two sides of 
_ the same animal, as shown in fig. 2. 
Inferior Lateral Cartilage (figs. 1 and 2, 7. J. c.).—Also consists of soft cartilage, and 
widens considerably in front to fuse with the ventro-posterior border of the hyoid arch, 
the latter at this region being likewise formed of soft cartilage. The inferior lateral 
courses almost straight backwards on the ventral wall of the pharynx, and between it 
and the posterior segment of the basal plate, but slightly external to the latter. It 
passes internal to the first branchial arch without however being in any way connected 
with it, and by its dorsal border fuses behind with the ventral extremity of the upper 
division of the second branchial arch. The inferior lateral cartilage may terminate in 
this way, as shown in fig. 2, or, as perhaps is more generally the case, and as in 
Bdellostoma, it may be extended beyond the second branchial arch as a tapering rod 
coursing upwards on the /ateral surface of the pharynx, where it terminates after a 
shorter course than the superior bar. Neumayer figures its absence behind the second 
branchial arch, but its presence here is shown by P. Ftrprincer and Parker. I have 
added it in fig. 1 (although it was not present in the specimen from which the drawing 
was made) in order that both conditions may be represented. 
“ Branchial” Arch 1 (figs. 1 and 2, br. a.').—This is of soft cartilage in Myaine but 
of hard in Bdellostoma, according to J. Mttuer. It arises dorsally, as above described, 
from the superior lateral cartilage, and courses in a half-ring round the lateral wall of the 
pharynx, bending first backwards and then forwards over the inferior lateral cartilage. 
It finally fuses with the lower division of the second branchial arch, when this is present 
(fig. 1), and at once becomes gradually merged into the hard cartilage of the middle 
seoment of the basal plate, as elsewhere described. 
“ Branchial” Arch 2 (figs. 1 and 2, br. a.*).—Formed of soft cartilage. There is a 
somewhat surprising variation in this arch, since the lower division is not always 
present. It was, for example, undoubtedly absent in the specimen on which figs. 1 and 
2 were based ; but I have found it in others. It was not found by Parksr in Myzine, 
but is figured by P. FUrRBRincER and Neumayer, and it is present in all my series of 
sections without exception.* | have therefore added it in fig. 1, which may in this respect 
be compared with fig. 2. This lower division of the arch, after fusing in front with the 
first branchial, passes backwards at the side of and external to the dorsal boundary of 
the posterior segment of the basal plate, finally rising slightly above the latter to 
terminate freely at about the level of the extremity of the superior lateral cartilage. 
Ayers and Jackson describe in Bdellostoma a fusion of the posterior extremity of the 
* In two museum preparations made by Fric of Prag, it was present in one and not in the other. 
P My 8, p 
