HAG-FISHES. 
1197 
In the head of Myxine the cartilaginous skeleton 
is comparatively far more developed and complex. Here 
we meet with two kinds of cartilaginous tissue, one 
rather hard, of a yellowish colour, the other soft, colour- 
less. This cartilage forms the floor of the cranium, as 
well as a number of processes and arches originating 
therefrom and composing a singular framework or 
“basket-work” within the head. No segmentation into 
vertebral parts can be observed, as we have already 
stated ; but by means of a comparison with Petromy zon 
and its larval form and, above all, with the phenomena 
during the development of amphibian larva?, it has 
been attempted, not without success, to interpret in 
detail the cartilaginous framework of the skull in 
My xine. Following Parker’s explanation we here give 
a brief description (fig. 355). 
The anterior conical termination of the notochord 
is surrounded by a sheath of hard cartilage (the para- 
chordal cartilage or investing mass, fig. 355, h), which 
in the median line exhibits a dorsal fissure and on 
the sides passes into the rounded kidney-shaped audi- 
tory capsules (c), also formed of hard cartilage, which 
have their longitudinal axes directed from within and 
behind outwards and forwards, and present on their 
inner superior side the foramina for the branches of 
the auditory nerve. In front the parachordal cartilage 
passes into two slender cartilaginous rods, the so-called 
cranial trabeculce (d), which enclose an elongate oval 
hole (the basicranial fontanelle, e ) composing the floor 
of the cerebral cavity and in great part filled by fibrous 
connective tissue, but containing behind and in the 
middle a spoon-shaped cartilage (the posterior intertra- 
becula, /). Anteriorly the trabecula? pass on each side 
into the palatine cartilages (g), which, together with 
the ethmoid cartilage ( h ) joining them to each other 
in front, form the anterior limit of the fontanelle. From 
the anterior ends of the palatine cartilages projects on 
each side a cartilaginous rod ( cornu prcepalatinum, i ), 
curved outwards and forwards and pointed at the tip. 
True cornua trabecularmn are wanting. In the median 
line lies a long cartilaginous rod (the anterior inter- 
trabecula, k) originating from the dorsal side of the 
anterior termination of the fontanelle and from the 
ethmoid region. This rod supports the long tube, 
formed of transversal cartilaginous rings, that com- 
poses the nasal duct ( l ) and leads behind partly to the 
olfactory organ, partly to the palate, into the cavity 
of which it has a free opening. On each side of the 
fore end of the anterior intertrabecula and the anterior 
opening of the nasal duct are two pairs of short, some- 
what curved, anteriorly pointed rods of cartilage (m), 
which are the supports of four — two on each side of 
the nasal aperture — tentacles or papilla? (“barbels”). On 
the outer side each of the two trabeculae is bounded by 
an elongate oval hole ( fenestra suborbitalis, n) and on the 
outside of the latter is another cartilage ( pterygoideum , 
o), which here forms the outer edge of the cartilaginous 
framework of the skull and behind borders on another, 
larger hole ( fenestra lateralis anterior, p), also of an 
elongate oval shape. On the inner side of this fenestra 
Fig. 355. Skull of Myxine glutinosa, seen from below, X 5. 
After Parker. 
a, notochord; b, parachordal cartilage; e, auditory capsules; il , trabe- 
culae ; e, basicranial fontanelle; f, posterior intertrabecula; g , palatine 
cartilage; h, ethmoid cartilage; lit, ethmoidal tooth; i, cornua prae- 
palatina; k, anterior intertrabecula; l, nasal duct (in outline); m, carti- 
laginous rods of the four circumnasal tentacles; n, suborbital fenestra; 
o, pterygoideum; p, anterior lateral fenestra; q, rnandibulo-hyoid 
fenestra; r , quadrature ; s, symplectic region; t, interhyoideum ; u, epi- 
hyoideum; v, ceratohyoideum, x, first epibranchial ; y, posterior lateral 
fenestra; z , first pharyngobranchial; a, second pharyngobranchial. 
