Range extension for the region of sympatry between the nudibranchs Hermissenda opalescens and Hermissenda crassicornis in the northeastern Pacific oleh Emily M. Merlo, Kathryn A. Milligan, Nola B. Sheets, Christopher J. Neufeld, Tao M. Eastham, A.L. Ka’ala Estores-Pacheco, Dirk Steinke, Paul D.N. Hebert, Ángel Valdés, Russell C. Wyeth