Maestricht monitor
definition: The Mosasaurus Hofmanni. See Mosasaurus.

Maestricht monitor is an 18 letter word that begins with an M and ends in an R

Magneto-electrical (a.)
definition: Pertaining to
Or characterized by electricity by the action of magnets; as magneto-electric induction.
Magneto-electrical is an 18 letter word that begins with an M and ends in an L

Maxillo-mandibular (a.)
definition: Pertaining to the maxilla and mandible; as
The maxillo-mandibular nerve.
Maxillo-mandibular is an 18 letter word that begins with an M and ends in an R

Mechanico-chemical (a.)
definition: Pertaining to
Connected with or dependent upon both mechanics and chemistry; -- said especially of those sciences which treat of such phenomena as seem to depend on the laws both of mechanics and chemistry as electricity and magnetism.
Mechanico-chemical is an 18 letter word that begins with an M and ends in an L

Micaceo-calcareous (a.)
definition: Partaking of the nature of
Or consisting of mica and lime; -- applied to a mica schist containing carbonate of lime.
Micaceo-calcareous is an 18 letter word that begins with an M and ends in an S

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