They sound exactly like fleas, even thought they don't match the descriptions you've read.
They're about the size of a pin head, or about the size of the comma used in this text. They are black or dark brown in color and have "hard shells," as you describe. They jump and they're quick. And they can bite people to where the bite could be mistaken for a mosquito bite. They also put your dog at risk of getting tapeworm, which are a pain to get rid of.
Do you keep prescription flea/tick treatment on your dog, such as Frontline or Advantix? If not, get some from your vet and those bugs will be gone from your dog within about 48 hours.
Don't use flea/tick treatment from the grocery or pet stores, like Hartz or Sergeants. They don't work. You need Frontline or Advantix.