EXTERNAL ANATOMY OF THE VERTEBRATES ' (1) 



A. Cyclostomata 



1. Examine a Lamprey (Petromyzon marinus) and note the long cylin- 

 drical eel-shaped body covered with a soft slimy skin which entirely lacks 

 rigid exoskeletal structures. Identify the anterior, posterior, dorsal, 

 and ventral surfaces. Note: (a) the jawless mouth which lies at the 

 bottom of (6) the suctorial buccal funnel with (c) a number of horny 

 teeth on each side. Note further (d) a pair of large eyes, and between 

 them on the dorsal surface of the head (e) a single olfactory opening 

 (nasal aperture). Laterally and posteriorly to the eyes, on each side 

 of the body, are (/) seven gill slits opening through the body wall. 

 Locate (g) the urogenital aperture near the posterior end of the body. 

 Examine the unpaired fins on the dorsal and ventral surfaces and around 

 the tail region. Draw in outline to show general structure. 



B. Pisces, or Bony Fishes 



2. Examine a small specimen of some common Bony Fish and note the 

 pointed, laterally compressed body adapted for rapid swimming, with a 

 well-developed head, trunk, and tail. Identify the anterior, posterior, 

 dorsal, and ventral surfaces. Examine (a) the overlapping scales which 

 almost completely cover the body. Note: (6) the large mouth with 

 (c) upper and lower jaws and (d) numerous teeth. Note further (e) the 

 eyes; (/) the paired dorsal olfactory openings; and (g) the oper- 

 culum covering the gills on each side of the body. Examine : (h) the 

 fins and identify the two unpaired dorsal fins ; the caudal fin with 

 dorsal and ventral lobes (homocercal) ; the single ventral fin ; and, 

 finally, the two pairs of paired fins, namely the pectoral fins, one 

 on each side of the body just back of the operculum, and the pelvic 

 fins, attached to the ventral surface. Draw in outline to show general 

 structure. 



C. Amphibia 



1. Examine a Frog and note: (a) the general form of the animal; 

 (b) the division into head and trunk; (c) the fore and hind limbs; 



l B. pp. 152-157; 164-167. 

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