1127 



PLAGIOSTOMI SELACHOIDEP. 



Pectoral fins of ordinary form, situated behind or belon- the branchial apertures. Tail gradually contracted in 

 unbroken continuity with the trunk. Anal fin present or u-anting. One or two dorsal fins, the anterior generally 



belonging to the abdominal portian of the body. 



Among tlic Sliai'ks iiistaiK-es are indeed afforded 

 of coin})aratively slii.ii'gish l)ottoui-fislies; but this sub- 

 order consists ])riiici|)ally of the most powerful and 

 endui'iiig swimmers, which chase their l^rey in speedy 

 pursuit and seize it with dexterous agility. Their form 



bod\' and uiorc pointed fins. 1-^speciali)' their caudal 

 tin, the propeller of the body, is in general powerfully 

 developed and, in contradistinction to that of the Rays, 

 principall}' ventral (lieterocercal). 



The sensory organs of the Sharks are also adapted 



of body adapts itself to their manner of life. The rpiiet to the re(|uirements of their predatory existence. The 



Fig. 325. Diagram showing the ramification of the cranial nerves and the system of the hiteral line in tijc anterior part of a Greenland 



Shark {Acanthorhinus carcharias). After Ewart. 

 aq, aquceductus vestibuli; Au, auditory nerve; bu, buccal branch of the facial nerve; cgU ciliary ganglion; Fa, roots of the facial nerve; 

 /a, facial nerve proper; Gl, glossopharyngeal nerve; gbu, ganglion of the buccal branch; ggl, ganglion of the glossopharyngeal nerve; g. hit, 

 ganglion of the intestinal branch of the nennis vagun; g. Vag*, ganglion of the fourth branch of the tierviis vagus; lim, ganglion of the 

 hyomandibular branch of (he facial nerve; hya, hyoid ampullae; lab, labyrinth; tra, lateral ampull;e of the snout; ma, mandibular ampullie; 

 md, mandibular branch of the trigeminal nerve; m,v, maxillary branch of the trigeminal nerve; JV, nasal cavity; n. int, iutestinal branch of 

 the nerviis vagus; n. tat, lateral branch of the tiervus vagus; o, mouth; oa, oral ampullie; Oc, eye; om, oculomotor nerve; pb, last prebrauchial 

 division of the ttervus vagus; ph, Inst 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): Ra, superior rostral ampullar; sof, superficial ophthalmic branch of the facial nerve; sot, superficial ophthalmic branch 

 of the trigeminal nerve; S]>, spiracle; Tr, trigeminal nerve; Vag^ — ^, first — fifth branches of the nervus vagus; 1 — 27, canals of the system 

 of tlie lateral line. The signification of these numerals is explained below fig. 308, see above, p. 1091. 



and indolent Sharks iia\e a more depressed body — an- system of tlie lateral line (see the explanation of fig. 

 teriorly at least — and more rounded fins; the active 325) consists of the same divisions as in the Rays, 

 and more distinctly raptatorial a more terete, fusiform . only that here the opercular (hyomandibular) canal 



" From the Greek Oe/.a/o^;, a cartilaginous fish 

 Scandinavimi Fishes. 



