ELASMOBEANCHS. 
1065 
A and 295) never forms a closed arch, but only a 
centrally situated half-arch on each side, the two halves 
being usually confluent in the median line of the belly, 
but. in the Chimaeras united only by a mobile sym- 
physis. The main part of the pelvic girdle — originally 
produced by the inward growth and coalescence of the 
inner (proximal) parts of the primary ventral radialia - 
answers to the ossa pubis and ossa iscliii of the higher 
vertebrates, but in most cases there appears on each 
side a process ascending from the end of the pelvic 
disk, especially well developed iu the Rays, and re | we- 
an d the aponeurosis of the lateral muscles, in the same 
manner as the suprascapular cartilage suspends the 
shoulder-girdle in these fishes and in the . Sharks. A 
closer morphological connexion in respect to the struc- 
ture of the shoulder-girdle and pelvis exists, as we see, 
between the Elasmobranchs and the higher vertebrates 
than between the former and the Teleosts. 
The structure of the tins points to a similar con- 
clusion. In this respect, it is true, (he Elasmobranchs 
approach nearer to the common parent-forms, where 
all the fins were more or less differentiated sections of 
Fig. 294. Anterior part of the skeleton in a ( 'J hi nicer a monstrosa , a 71 . 2 / 3 nat. size. 
b, saddle-like disk formed by the coalescence of the neurapophyses of the first abdominal vertebrae; bhy, basihyoid ; ce, anterior aperture of the 
ethmoidal canal; ch , notochord; chy, ceratohyoid; cp, preorbital canal, passage of the ramus ophthalmicus superior nervi trigemini to the 
ethmoidal canal; da, anterior dental plate of the upper jaw; di, dental plate of the lower jaw; dp, posterior dental plate of the upper jaw; 
fa, foramen for a branch of the facial nerve; fb , fibrils of the anterior dorsal and the pectoral fins; h, rudimentary haem apophyses ; hm, hyo- 
mandibular; iktd, spine (ichthyodorulite) of the anterior dorsal fin; in, interneurals; If, fronto-nasal cartilage (prehensile organ of the male): 
Imi, labial cartilage of the lower jaw; Ims, labial cartilage of the upper jaw; hij, first labial cartilage of the nasal capsule; ln 2 , second labial 
cartilage of the nasal capsule; lr i , first rostro-nasal cartilage; /;%>, second rostro-nasal cartilage; mb, posterior, fibril-less membrane of the first 
dorsal fin; mp, mesopterygiuvi ; mt ,, first part of the metapterygium; mt 2 , second part of the metapterygium; N, nasal capsule; na, neurapo- 
physes; occ, occipital condyles; on, orbitonasal canal, passage of the ramus ophthalmicus profundus nervi trigemini to the ethmoidal canal; 
opt, optic foramen; pp, propterygium; qpg , palatoquadrate; Ii, undivided radial (interspinal) cartilage of the first dorsal fin; rb, foramen for 
the ramus buccalis nervi trigemini ; s, Solgerian (spiracular) cartilage; sc, scapular cartilage; sp, tegumentary cartilage of the spinal canal 
( processus spinosi superior es) ; ssc , suprascapular cartilage; sy, symplecticum; tr, foramen for the trigeminal and facial nerves; trs, foramen 
for the ramus ophthalmicus nervi trigemini: 1 — 6, first (proximal) to sixth (distal) series of the pectoral radialia. 
senting an os ilii. In the Chimaeras this process runs 
so far up, more in a straight line with the pelvic disk, 
as to unite by means of ligaments the pelvic girdle 
originally continuous dermal folds — unpaired along the 
dorsal and inferior caudal margins, but double (paired)' 
on the ventral side, as having been divided to surround 
