Time to take a deep breath before we plunge into the often-confusing world of citrus taxonomy, but I'll give the short answer first :-)
The red mandarin your your kit is organic and from Italy, where they designated it C. nobilis. When you observed that your oil from Eden smelled different (and was labeled C. reticulata) the main reason it smelled different was that it was from a different country, and may not be organic. Your textbook covers terroir and the factual elements that make oils vary from year to year, supplier to supplier, country to country. Forces of nature and man can cause the oils to differ. That, plus, with the citruses, the confusing taxonomy.
The taxonomy and systematics of the genus are complex and the precise number of natural species is unclear, as many of the named species are hybrids clonally propagated through seeds (by apomixis), and there is genetic evidence that even some wild, true-breeding species are of hybrid origin.
All this made me whimper a bit as I studied citrus as one of the world's largest citrus research centers at the University of California, Riverside (UCR).
I'll let you all wade through the following links if you wish. Hopefully, my information about terroir (in the textbook) will partially solve the question. You will see that C. nobilis and C. reticulata are *sometimes* used interchangably. Sometimes nobilis can mean tangerines and other peel-able citruses, like naval oranges. In the past, it was also used for mandarins, and the hybridization between the two sp. is where I get lost, frankly. I let my nose guide me.
Here's the funny part: at UCR I learned some of us are genetically programmed to be sensitive to a bitter glycoside in some citruses, particularly grapefruits and the mandarin/tangerines. I'm one of them. It's the reason a lot of people can't tolerate the taste of grapefruit. To me, cut grapefruits smell like a petroleum products, like car tires, you know, the overwhelming smell of rubber/plastic when you walk into a tire shop. Yuk. However, I love the smell of grapefruit oils. Now, here's the weird part: all mandarins have a smell of dead mouse to me. The first second or two, I get the lovely citrus scent, but then, wham, dead mouse.
That last bit doesn't have anything directly to do with the student's confusion about the mandarins smelling differently, I just wanted to throw that in to let you know that we're all very different biological organisms, with 99.9% of our genetic material in common, but that .1% can be very interesting. BTW, the dead mouse smell disappears when I use mandarin in a blend, it's just the undiluted oil.
Now, don't get me going on vetiver. On my skin, not on a scent strip, it smells so sickly sweet it makes me ill. No matter what type, from any country. Terroir doesn't count here, I just have a body chemistry that interacts with vetiver in a very nauseating way (to me).
Here are some utterly confusing citrus links!
http://tinyurl.com/bcvdn3w scroll down a little on this page and you'll see:
http://www.hort.purdue.edu/newcrop/morton/index.html This is an incredible, free online book, written by my role model, Julia Morton, economic botanist. Look under Rutaceae for the citrus family.
Have fun exploring the fragrant, delicious, confusing world of citrus! Always sample before purchasing, and alway refer to your existing stock to compare and your organoleptic evaluation notes, and you'll be more able to purchase the correct replacement oil.