这是我最好的尝试:
CSS
.map_infobox {
margin: 30px 0 0 30px;
position: relative;
background: #FFF;
border-radius: 10px;
width: 250px;
height: 250px;
border-opacity: 0.3;
border: 5px solid rgba(0, 0, 0, .2);
-webkit-background-clip: padding-box; /* for Safari */
background-clip: padding-box; /* for IE9+, Firefox 4+, Opera, Chrome */
}
.map_infobox:before{
content: "";
position: absolute;
top: 50%;
left: -35px;
z-index: 1;
height:60px;
width:30px;
margin-top: -15px;
background: linear-gradient(-45deg, white 17px, rgba(0,0,0,0.2) 17px, rgba(0,0,0,0.2) 21px, transparent 21px), linear-gradient(225deg, white 17px, rgba(0,0,0,0.2) 17px, rgba(0,0,0,0.2) 21px, transparent 21px);
background-position: left 0px, right bottom;
background-size: 100% 50%;
background-repeat: no-repeat;
}
.map_infobox:after{
content: "";
position: absolute;
top: 50%;
left: -35px;
z-index: 1;
height: 48px;
width:30px;
margin-top: -14px;
border-right: solid 5px white;
border-top: solid 5px transparent;
border-bottom: solid 5px transparent;
}
fiddle