SHARKS. 
1127 
PLAGIOSTOMI SELACHOIDEI”. 
Pectoral fins of ordinary form , situated behind or below the branchial apertures. Tail gradually contracted in 
unbroken continuity with the trunk. Anal fin present or wanting. One or two dorsal fins, the anterior generally 
belonging to the abdominal portion of the body. 
Among the Sharks instances are indeed afforded 
of comparatively sluggish bottom-fishes; but this sub- 
order consists principally of the most powerful and 
enduring swimmers, which chase their prey in speedy 
pursuit and seize it with dexterous agility. Their form 
of body adapts itself to their manner of life. The quiet 
body and more pointed fins. Especially their caudal 
fin, the propeller of the body, is in general powerfully 
developed and, in contradistinction to that of the Rays, 
principally ventral (heterocerca.1). 
The sensory organs of the Sharks are also adapted 
to the requirements of their predatory existence. The 
Fig. 325. Diagram showing the ramification of the cranial nerves and the system of the lateral line in the anterior part of a Greenland 
Shark ( Acanthorhinus carcharias). After Ewart. 
aq, aquceductus vestibuli; Au , auditory nerve; bu , buccal branch of the facial nerve; cgl, ciliary ganglion; Fa, roots of the facial nerve; 
fa, facial nerve proper; Gl , glossopharyngeal nerve; gbu, ganglion of the buccal branch; ggl, ganglion of the glossopharyngeal nerve; g. int, 
ganglion of the intestinal branch of the nervus vagus; g. Vag 4 , ganglion of the fourth branch of the nervus vagus ; Inn, ganglion of the 
hyomandibular branch of the facial nerve; by a, hyoid ampullae; lab, labyrinth; Ira, lateral ampullae of the snout; ma, mandibular ampullae; 
md, mandibular branch of the trigeminal nerve; mx, maxillary branch of the trigeminal nerve; N, nasal cavity; rt. int, intestinal branch of 
the nervus vagus; n. lat, lateral branch of the nervus vagus; o, mouth; oa, oral ampullae; Oc , eye; ora, oculomotor nerve; pb, last prebranchial 
division of the nervus vagus; ph, last pharyngeal branch of the nervus vagus; pi, palatine branch of the facial nerve; po, pit organs; Pr and 
pr, nervus ophthalmicus profundus; ptb, last postbranchial division of the nervus vagus', ptbf, postbranchial division of the facial nerve (running 
behind the spiracle): Pa, superior rostral ampullae; sof, superficial ophthalmic branch of the facial nerve; sot, superficial ophthalmic branch 
of the trigeminal nerve; sp, spiracle; Tv, trigeminal nerve; Vag ] — °, first — fifth branches of the nervus vagus; 1 — 27, canals of the system 
of the lateral line. The signification of these numerals is explained below fig. 308, see above, p. 1091. 
and . indolent Sharks have a more depressed body — an- 
teriorly at least — and more rounded fins; the active 
and more distinctly raptatorial a more terete, fusiform 
system of the lateral line (see the explanation of fig. 
325) consists of the same divisions as in the Rays, 
only that here the opercular (hyomandibular) canal 
a From the Greek oslayog, a cartilaginous fish. 
Scandinavian Fishes. 
142 
