Biologists pronounce the ae on the end of Lamnidae as a ee .  
They also pronounce a ch combination in the Greek/Latin scientific names  as a hard K.

Assigning sharks to a family is an arbitrary decision. ( Matter of opinion)  It is just a convenient way of grouping them for study.  There are 34 shark families total.  Some families have only one member, some several, some dozens.  

The Lamnidae family has five very interesting members.   This is a good family to be aware of since three of its members;  the white, shortfin mako and porbeagle, are found in our New England waters.  

The white and the mako are celebrity sharks.  Both are well know all over the world. The white for its interaction with swimmers and surfers, and the shortfin mako for its interaction with anglers and boaters.  ("Interaction" is a euphemism for: nasty and sometimes fatal encounters.") 

Unique biological characteristics are the deciding factors as to which family a shark will be assigned.  Looking alike won't necessarily get you in the same shark family.  The blueshark, lemon, bull and tiger sharks are all members of the much larger 53 member Carcharhinidae family, and those species don't look anything alike in color, fin structure or body shape, There is no way you could mistake one for the other.  Some others in that family look very much alike and are hard to tell apart, like the sandbar and dusky sharks.  

There are 8 Orders of sharks. The  Order Lamniformes, has  15 shark species, placed into7 families.   Characteristics they would share in common are: Having an anal fin - 2 dorsal fins without spines - mouth extends back behind eyes  - no nictitating membrane to protect the eyes.  We are going to take a look at one of those 8 families, know as the Lamnidae family.

Porbeagle: Lamna nasus -In the New England area, possibly year round.  They look somewhat like a small white, or a chubby mako.  They have a white strip or patch on the back bottom of the dorsal fin and a secondary keel on the tail. The teeth have protrusions at the base and the teeth are not serrated.

Salmon shark: Lamna ditropis - not here.  It is on the West Coast and Alaska-referred to in older literature as the Pacific Porbeagle.   Lacks a white patch on the dorsal, and has very noticeable dark spots on its white underside, and a shorter snout than our porbeagle, Lamna nasus.   It has  the same type of teeth, which have protrusions at the base and are not serrated.  Small salmon sharks may not have the dark spots on the bottom side as do the adults.

Shortfin Mako: Isurus oxyrinchus - In the New England area, a great jumping game fish. The area under the lower jaw will be white, where as the longfin mako will have a dark area under the jaw.  Very fast!   Very dangerous to anglers! And record size, in New England waters.

Longfin Mako: Isurus paucus - not here in coastal New England, a rare species anywhere.  When hooked, a jumper like the shortfin mako.  Found well offshore of our south eastern states, and in Cuban waters.  Like the tiger, Galeocerdo cuvier, the longfin may follow the Gulf Stream northward but pass well to our south east.   It has long swept back pectorals, and the area under its lower jaw is dark.   Its eyes are larger than those  of the   shortfin mako.  Its meat is not as tasty as the shortfin. It appears it does not have as good a system for bringing warm blood back to the muscles as the other members of this family. But not much research has been done done on this rare species. 
The longfin mako is now a protected species.