764 MR FRANK J. COLE 
lower division with the inferior lateral cartilage, which eliminates the break in the course 
of the arch. As this fusion was not found by J. MULLER or PaRKER in Bdellostoma, and 
has never been seen in Myaxzne, it must represent another and an important variation in 
the structure of the arch. The wpper division of the second branchial arch is very 
short; it fuses above and below with the superior and inferior lateral cartilages, as 
above described, and in one series of sections despatched forwards in front a blunt 
process similar to that figured and: described in Bdellostoma by AyERs and JACKSON. 
As, however, this seems to be not of general occurrence, I have not introduced it into 
the figures. 
“ Hyoid” Arch (figs. 1 and 2, hy.).—The connections of this arch above and below 
with the auditory capsule and superior and inferior lateral cartilages, have been already 
described. Dorsally in front, it fuses also with the hard cartilage of the posterior 
extremity of the superior process of the pterygo-quadrate, and similarly below 
and in front with the inferior process of the pterygo-quadrate. The hyoid arch is short 
but wide, and is bent round the lateral wall of the pharynx, lying just external to it. 
It is composed of hard and soft cartilage, distributed as shown in figs. 1 and 2. 
According to PARKER, it consists almost entirely of soft cartilage in Myaine and of 
hard in Bdellostoma ; but I have succeeded in confirming the distribution of the two 
kinds of cartilage shown in my figures in serial sections, and, further, PaRKER’s own 
sections do not bear out his dissections. Posteriorly, the hyoid arch sends backwards a 
broad, blunt process of soft cartilage, which projects into the fourth fenestra of the skull, 
as in Bdellostoma. Anteriorly, a corresponding process, although a very slight one, is 
despatched forwards into the third fenestra, which represents the much more extensive 
process in Bdellostoma described by Parker and Ayers and Jackson, but not found 
by J. Mtxuer. In one series of sections, the ventral margin of soft cartilage at the 
region of the junction of the hyoid with the inferior process of the pterygo-quadrate 
sent downwards and forwards a blind rod of cartilage ; but this seems to be a variation 
of little importance, beyond that it is one of the numerous examples of the sporadic 
appearance of soft cartilage in the connective tissues of Myxine generally. It is, 
however, also figured by NEUMAYER. 3 
The posterior boundary of the hyoid assists the superior and inferior lateral 
cartilages, and the upper division of the second branchial arch, in forming the large 
and somewhat irregular fourth fenestra of the skull (f*), whilst its anterior border 
forms the posterior boundary of the third fenestra (f°). 
‘« Pterygo-quadrate” (figs. 1 and 2, p. g.).—This is a tri-radiate structure formed 
mostly of hard cartilage. It sends upwards and forwards a thick bar or anterior 
process which forms the ventral or external boundary of the first fenestra (f''), and 
fuses in front with the zone of soft cartilage (absent in dellostoma, according to 
PaRKER) forming the posterior extremity of the palatine bar. The second one is the 
superior process, which, with the anterior process, forms the subocular arch of AYERS 
and Jackson. ‘The superior process passes backwards and slightly upwards to complete 
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