In geology, a key bed ("syn" marker bed) is a relatively thin layer of sedimentary rock that is readily recognized on the basis of either its distinct physical characteristics or fossil content and can be mapped over a very large geographic area.
 As a result, a key bed is useful for correlating sequences of sedimentary rocks over a large area.
 Typically, key beds were created as the result of either instantaneous events or (geologically speaking) very short episodes of the widespread deposition of a specific types of sediment.
 As the result, key beds often can be used for both mapping and correlating sedimentary rocks and dating them.
 Volcanic ash beds (tonsteins and bentonite beds) and impact spherule beds, and specific megaturbidites are types of key beds created by instantaneous events.
 The widespread accumulation of distinctive sediments over a geologically short period of time have created key beds in the form of peat beds, coal beds, shell beds, marine bands, black shales in cyclothems, and oil shales.
 A well-known example of a key bed is the global layer of iridium-rich impact ejecta that marks the Cretaceous–Paleogene boundary (K–T boundary).
In the United States and Canada, a diamond lane is a special lane on a street or highway that is reserved for specific types of traffic.
 These lanes are usually marked with white diamonds or lozenge, hence their name.
 Diamond lanes are generally the right-most or left-most lane on the road.
 They are usually implemented to provide ways through traffic congestion, for safety reasons, and to encourage environmentally friendly transportation.
 A diamond lane may be intended for a specific type of traffic, or for several types.
 The intended use of a diamond lane is marked by traffic signs.
 In most areas, violating the rules of a diamond lane is punishable by a fine.
A bridge bearing is a component of a bridge which typically provides a resting surface between bridge piers and the bridge deck.
 The purpose of a bearing is to allow controlled movement and thereby reduce the stresses involved.
 Movement could be thermal expansion or contraction, or movement from other sources such as seismic activity.
 There are several different types of bridge bearings which are used depending on a number of different factors including the bridge span.
 The oldest form of bridge bearing is simply two plates resting on top of each other.
 A common form of modern bridge bearing is the elastomeric bridge bearing.
 Another type of bridge bearing is the mechanical bridge bearing.
 There are several types of mechanical bridge bearing, such as the pinned bearing, which in turn includes specific types such as the rocker bearing, and the roller bearing.
 Another type of mechanical bearing is the fixed bearing, which allows rotation, but not other forms of movement.
The following is a list of rock types recognized by petrologists.
 There is no agreed number of specific types of rocks.
 Any unique combination of chemical composition, mineralogy, grain size, texture, or other distinguishing characteristics can describe rock types.
 Additionally, different classification systems exist for each major type of rock.
 There are three major types of rock, sedimentary, metamorphic, and igneous.
 They are all identified by their texture, streak, and location, among other factors.
.
Chrysanthemums ( ), sometimes called mums or chrysanths, are flowering plants of the genus Chrysanthemum in the family Asteraceae.
 They are native to Asia and northeastern Europe.
 Most species originate from East Asia and the center of diversity is in China.
 There are countless horticultural varieties and cultivars.
Generic programming is a style of computer programming in which algorithms are written in terms of types "to-be-specified-later" that are then "instantiated" when needed for specific types provided as parameters.
 This approach, pioneered by ML in 1973, permits writing common functions or types that differ only in the set of types on which they operate when used, thus reducing duplication.
 Such software entities are known as "generics" in Ada, C, C#, Delphi, Eiffel, F#, Java, Objective-C, Rust, Swift, and Visual Basic .
NET.
 They are known as "parametric polymorphism" in ML, Scala, Haskell (the Haskell community also uses the term "generic" for a related but somewhat different concept) and Julia; "templates" in C++ and D; and "parameterized types" in the influential 1994 book "Design Patterns".
 The authors of "Design Patterns" note that this technique, especially when combined with delegation, is very powerful, however, Dynamic, highly parameterized software is harder to understand than more static software.
A variety of treaties and agreements have been enacted to regulate the use, development and possession of various types of weapons of mass destruction.
 Treaties may regulate weapons use under the customs of war (Hague Conventions, Geneva Protocol), ban specific types of weapons (Chemical Weapons Convention, Biological Weapons Convention), limit weapons research (Partial Test Ban Treaty, Comprehensive Nuclear-Test-Ban Treaty), limit allowable weapons stockpiles and delivery systems (START I, SORT) or regulate civilian use of weapon precursors (Chemical Weapons Convention, Biological Weapons Convention).
 The history of weapons control has also included treaties to limit effective defense against weapons of mass destruction in order to preserve the deterrent doctrine of mutual assured destruction (Anti-Ballistic Missile Treaty) as well as treaties to limit the spread of nuclear technologies geographically (African Nuclear Weapons Free Zone Treaty, Nuclear Non-Proliferation Treaty).
This is a list of pen types, brands and companies.
 A pen is a handheld device used to apply ink to a surface, usually paper, for writing or drawing.
 Additional types of specialized pens are used in specific types of applications and environments such as in artwork, electronics, digital scanning and spaceflight and computing.
Mental calculation comprises arithmetical calculations using only the human brain, with no help from any other supplies, for example, a calculator.
 People use mental calculation when computing tools are not available, when it is faster than other means of calculation (for example, conventional methods as taught in educational institutions), or in a competitive context.
 Mental calculation often involves the use of specific techniques devised for specific types of problems.
Myrtus, with the common name myrtle, is a genus of flowering plants in the family Myrtaceae, described by Linnaeus in 1753.

Question: Myrtus and Chrysanthemum, are which mutual specific types?
Answer: flowering plants