Clojure defrecord, namespaces, and dashes vs underscores

gistfile1.clj

user=> (ns my-ns)
nil
my-ns=> (defrecord Outfit [shirt pants])
my_ns.Outfit
my-ns=> (ns clothes.outfit
   #_=>   (:require [my-ns])
   #_=>   (:import [my_ns Outfit])); note that we defined it in my-ns, but we have to use an underscore to import it
nil
clothes.outfit=> (Outfit. "t-shirt" "jeans")
#my_ns.Outfit{:shirt "t-shirt", :pants "jeans"}
clothes.outfit=> (ns clothes.outfit
            #_=>   (:require [my-ns])
            #_=>   (:import [my-ns Outfit])) ; if we try to import it with a '-', like we defined it, we get a ClassNotFoundException

ClassNotFoundException my-ns.Outfit  java.net.URLClassLoader$1.run (URLClassLoader.java:366)
clothes.outfit=>

Ya, this is weird. Why does it do this?