In its fresh form this chile is called a chilaca. It's generally 6 to 8 inches long and 1 to 1½ inches in diameter. The rich-flavored, medium-hot pasilla is a blackish-brown color, which is why it's also called chile negro. This chile is sold whole, and powdered. It's particularly good for use in sauces.
From The Food Lover's Companion, Fourth edition by Sharon Tyler Herbst and Ron Herbst. Copyright © 2007, 2001, 1995, 1990 by Barron's Educational Series, Inc.