I can't help you with the species. But if you mentioned the 35 foot power line because you are concerned about height --- Don't worry unless you plan on living another 200 years --- and probably not even then.
Gloria - you lost the tag? Coccothrinax are difficult to id without flowers, seeds and being an adult. Even then it is precarious. Who did you buy it from? What was the length of time between the pictures. If it is relatively fast for a Coccothrinax it could be C. alta or C. barbadensis. If it is fast and gets a real fat trunk then it is C. spissa.
Ron,
I have another Coccothrinax Barbadensis which I purchased from Claude. It should be interesting to compare the two as they mature. They are both planted very close together. I will post a picture of the other one soon.