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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 64, No. 6 
Studies on the systematics of dorid nudibranchs of the genus Rostanga have added many new 
species to the genus, primarily based on specimens from Australia and the Indo-Pacific (Rudman 
and Avem, 1989) and from southern Africa (Garavoy, Valdes and Gosliner, 2001). An additional 
three species of Rostanga have been described since then: R. ankyra from the deep Pacific (Valdes, 
2001); R. alisae Martynov, 2003, from the Russian Pacific; and R. crocea from Ghana (Edmunds, 
2011). Thus far, only a single species of Rostanga, R. pulchra MacFarland, 1905, has been 
described from the eastern Pacific, where it is kn own from Alaska to Chile (Camacho-Garcia, 
Gosliner and Valdes, 2005; Schrodl and Grau, 2006). The Galapagos Islands Rostanga sp. in Cama¬ 
cho-Garcia et al. appears to be a Diaulula sp., based on dissection of the radula (present study). 
Recently, the Family Fionidae has been radically revised, combining most species of Tergi- 
pedidae, Calmidae and Eubranchidae into a single family (Celia, Carmona, Ekimova, Chich- 
varkhin, Schepetov and Gosliner, 2016) and realigning many of the genera within the family. As a 
result, most species previously considered as members of Cuthona Alder and Hancock, 1855 were 
transferred to Tenellia Costa, 1866. Of the 39 species of Fionidae found on the Pacific Coast of 
North America (Behrens and Hermosillo, 2005), only 13 were sequenced in Celia et al. (2016). 
They include species in the genera Eubranchus {E. olivaceus (O’Donoghue, 1922)), Cuthona 
(C. nana (Alder and Hancock, 1842)), Tenellia (T. adspersa (Nordman, 1845), T. albocrusta (Mac¬ 
Farland, 1966), T. columbiana (O’Donoghue, 1922), T. flavovulta (MacFarland, 1966), T. fulgens 
(MacFarland, 1966), T. lagunae (O’Donoghue, 1926) and T. pustulata (Alder and Hancock, 1854)), 
Cuthonella (C. concinna (Alder and Hancock, 1843) and C. cocoachroma (Williams and Gosliner, 
1979)) and Fiona ( F. pinnata (Eschscholtz, 1831)). None of the species found within the Gulf of 
California have been investigated by molecular studies. Despite confirmation from molecular data, 
a series of morphological criteria for differentiating the members of the revised genera were pro¬ 
posed by Celia et al. (2016). 
Since the work of Behrens and Hermosillo several additional species of Fionidae (as Tergi- 
pedidae) from the tropical eastern Pacific have been described. Camacho Garcia et al. (2005) 
included six undescribed species of Cuthona, not included in Behrens and Hermosillo. Hermosil¬ 
lo and Valdes (2007) described three new species of Cuthona and one new species of Eubranchus. 
Cuthona destinayae Hermosillo and Valdes, 2007 was included in Behrens and Hermosillo as 
Cuthona sp. 4 and by Camacho Garcia et al. as Cuthona sp. 2. Cuthona millenae Hermosillo and 
Valdes, 2007 was included in Behrens and Hermosillo as Cuthona sp. 5 and in Camacho Garcia et 
al. as Cuthona sp. 8. Cuthona behrensi Hermosillo and Valdes, 2007 was included in Camacho Gar¬ 
cia et al. as Cuthona sp. 9. Eubranchus yolandae Hermosillo and Valdes, 2007 was not included in 
either of the above mentioned field guides. Cuthona riosi Hermosillo and Valdes, 2008 was includ¬ 
ed in Behrens and Hermosillo as Cuthona sp. 2. 
Methods 
Specimens of the two species described here were collected beginning in 1992 and most 
recently in March, 2017 at Bahia del los Angeles, Mexico. Specimens from the 1990s were pre¬ 
served in either 10% formalin or Bouin’s fixative for proper preservation of anatomical structures. 
The most recently collected specimen of Rostanga was preserved entirely in 95% ethanol for later 
molecular study. 
At the California Academy of Sciences, dissections were completed, and drawings of anatom¬ 
ical structures were accomplished using a Nikon SMZ-U binocular microscope with drawing tube. 
Buccal masses, containing the jaws, radula and connective tissue, were carefully extracted from 
specimens with the aid of a dissecting microscope and forceps. The mass was placed in 10% sodi- 
