1. Cartilaginous fishes
Class Chondrichthyes

2. Marine Fishes
Class Chondrichthyes – Cartilaginous fishes; with about 1000 different species, they
include the different species of sharks, rays, skates, and ratfish.
Cartilaginous fishes have well
developed jaws and teeth;
Typically have a ventral mouth;
and, have rough, sandpaper-like
skin because of tiny scales…
In fact, their teeth are simply
modified scales!!

3. Marine Fishes – Sensory System
Marine fishes have well developed nervous and sensory systems.
Many have a great sense of smell. Their nostrils open to olfactory
sacs on both sides of the head. Some sharks can detect
blood at concentrations as little as one part per million!
Fishes detect taste with their taste buds in their mouth, as well as
on their barbels (whisker-like organs found around the
mouths of some bottom dwelling fishes).
Most fish have a somewhat well developed sense of vision. Some
shallow water bony fishes have color vision, but most fishes
do not… also, focusing is done by moving the lens as supposed
to changing it’s shape…
Some cartilaginous fish have sensory organs around the head called
ampullae of Lorenzini. They can detect week electrical fields
that may be used for navigation, as well as for detecting prey.
Most fishes can also perceive sounds with their inner ear, and they can detect
changes in their position within the water column using their ear
stones or otoliths… (nerve cells detect changes in positioning).

4. Senses

5. Senses

6. Barbels – Atlantic Sturgeon

7. Marine Fishes – Sensory System (cont.)
Finally, many fish have a lateral line that allows them to sense vibrations in the
water…

8. types of caudal fin : (A) - Heterocercal, (B) - Protocercal, (C) - Homocercal, (D) - Diphycercal

10. Shark Diet Discovery Channel Videos:
The Ultimate Guide to Sharks: Shark Diet
Air Jaws: Sharks of South Africa: Shark Feeding Frenzy
Air Jaws: Sharks of South Africa: Filming Air Jaws

11. Shark Mating Discovery Channel Videos:
The Ultimate Guide to Sharks: Shark Mating
The Ultimate Guide to Sharks: Shark Birth and Maturation
Sibling cannibalism

12. Skates vs. Rays Different Orders Reproduction Tooth Structure
Rays are viviparous (live bearing) while skates are oviparous (egg laying), releasing their eggs in rectangular cases sometimes called "mermaid´s purses".
Tooth Structure
Although skates may have small teeth, those of rays are plate-like and adapted for crushing prey. 
Morphology
Skates normally have prominent dorsal fins while those of rays are absent or reduced in rays.
Although a few electric rays are capable of delivering a powerful electric shock and some sting rays have large, barbed stingers, in general, these docile animals pose no real threat to swimmers and divers.

13. Skate