Code

 Header...
 struct proj {
  float mass;
  float pos[2];
  float v[2];
  struct proj *next;
};

 struct proj* newproj(struct proj *f){
   ... 

»  struct proj *new;

»  new=malloc(sizeof *new);
»  new->next=f;
»  return new;
}

 int main(){
   ... 

»  struct proj *first=NULL, *p=NULL;

  // Allocate a list of four
»  first=newproj(first);
»  first=newproj(first);
»  first=newproj(first);
»  first=newproj(first);

  // Now manually remove the third (first->next->next)
»  p=first->next;
»  p->next=p->next->next;

»  return 0;
}