Edit in JSFiddle

  <div class="demo one"></div>
  <div class="demo two"></div>
  <div class="demo three"></div>
  <div class="demo four"></div>
  <div class="demo five"></div>
  <div class="demo six"></div>

.demo{
  background: #b4a078;
  margin-bottom: 30px;
  width: 200px;
  height: 150px;
}
.one{
   width: 150px; height: 75px; 
   border-radius: 50% / 100% 100% 0 0;
}
.two{
   width: 150px;
   height: 150px;
   border-radius: 100% 0 0 0;
}
.three{
  border-radius: 50% / 100% 100% 0 0;
}
.four{
   width: 100px;
   border-radius: 100% 0 0 0;
}
.five{
  width: 300px;
  border-radius: 50% / 0 100%;
}
.six{
  width: 300px;
  border-radius: 50% / 100% 0;
}