Last Updated: Oct 05, 2016 Views: 82
Those are good questions, since the terms are often used interchangeably. I consulted a couple of different sources (which each had their own subtle variations on the terms!). I will outline what I found citations for several books I looked at:
According to Murano Magic by Carl I. Gable:
mosaic glass is a general term that refers to patterned glass objects
murrina is "a process for producing an intricately patterned object by melding together murrina plaques ('murrine') that have been prepared previously. The resulting matrix can be shaped directly into a form or, alternatively, be blown as a vessel. The murrine themselves are created by first melding rods or other small pieces of glass together in a mold, then slicing the varicolored result horizontally to display the colorful cross-section."
According to Giovanni Sarpellon's book Miniature Masterpieces: Mosaic Glass 1838-1924, however, the terms are used in a slightly different way:
First of all, Sarpellon clearly does identify murrine as a 19th century term, created to describe the reproductions of ancient mosaic glass by Italian glassmakers such as the Venice & Murano Glass company. He describes the technique of creating "mosaic glass" as much older and describes the different types of canes created over the years. He seems to be using mosaic glass and murrine somewhat interchangeably with a preference for mosaic glass for the general technique and then using the specific type of murrine being produced to describe it further.
I definitely don't feel qualified to answer this 100 percent--see what you think. The differences are subtle, but I think your original assessment seems correct to me, based on how these terms are used.
Let me know if you think you need further expert opinion than can be found in books and I can consult someone who has studied Italian glassmaking.