My blog entry showing a huge group of cownose rays prompted the question of the proper term for such a gathering. Most people are at least tangentially familiar with James Lipton's book "An Exaltation of Larks," which lists the appropriate collective terms for groups of animals and birds. As I searched the web regarding the rays, I couldn't find a consistent term for that species.
Then, to my consternation, the Random House Dictionary didn't even offer a definition of the word "venereal" to refer to a collective term for groups of creatures. So I went to what I consider the "gold standard" - the OED - and to my amazement, "venereal" is defined only in sexual terms or in relation to the planet Venus. "Venery" is there as a word related to the hunt or chase (which is where the collective terms first developed), but "venereal is curiously absent.
But back to the rays. There are a variety of links on the web listing venereal terms for different groups. THIS ONE covers some mammals, birds, reptiles, and fish. THIS list extends to people and things. This Wordinfo site is excellent, though their list seems to terminate at the letter "F." This list includes humorous contrivances, and this one has accumulated 765 entries.
The modern offerings are more fun than the traditional ones. Consider...
a column of accountants
a hive of allergists
a slew of assassins
a "heard" of audiologists
a rash of dermatologists
But nary an offering on any of those sites for a large group of cownose (or other) rays.