PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 64, No. 6, pp. 117-130, 6 figs., 1 table. October 31, 2017 
Two New Species of Nudibranch Mollusks from the 
Tropical Eastern Pacific of Mexico 
Terrence M. Gosliner 1 and Hans Bertsch 2 
1 Department of Invertebrate Zoology, California Academy of Sciences, 55 Music Concourse Drive, 
San Francisco, CA 94118, U.S.A. E-mail: tgosliner@calacademy.org; 
2 192 Imperial Beach Blvd., Imperial Beach, CA 91932, U.S.A. E-mail: hansmarvida@sbcglobal.net 
Two new species of nudibranch gastropods are described from the Bahia de los 
Angeles region of the Sea of Cortez, Baja California, Mexico. Rostanga ghiselini sp. 
nov. is known from two specimens found 25 years apart. It is immediately recogniz¬ 
able and distinct from all other Rostanga species by its bright red coloration with 
large densely packed black spots and conical rhinophores with transverse lamellae. 
Internal differences, especially the form of the bifurcate radular teeth, also distin¬ 
guish this species. Differences between R. ghiselini and the sympatric R. pulchra are 
noted. Tenellia ivetteae sp. nov., known from Mexico and Costa Rica, is characterized 
by a uniformly translucent white body with light yellowish pigment occupying the 
digestive gland of the cerata. The cerata are short and rounded. The uniseriate radu- 
la teeth have 4-7 elongate denticles on either side of the wide central cusp. The penis 
is armed with a short cuticular stylet. 
Se describen dos especies nuevas de gasteropodos nudibranquios de la Bahia de los 
Angeles en la region del Mar de Cortes, Baja California, Mexico. De Rostanga ghis¬ 
elini sp. nov. se conocen dos especimenes que fueron encontrados durante a lo largo 
de 25 anos. Esta se reconoce inmediatamente y se le distingue de las otras especies de 
Rostanga por su coloracion rojo brillante con grandes manchas de puntos negros 
agrupados densamente, y rinoforos conicos con lamelas transversales. Las diferen- 
cias internas, en especial la forma bifurcada de los dientes radulares, tambien es algo 
que distingue a esta especie. Se describen las diferencias entre R. ghiselini y su sim- 
patrica R. pulchra. Tenellia ivetteae sp. nov., conocida desde Mexico y Costa Rica, se 
caracteriza por su cuerpo bianco uniformamente translucido con pigmentos amaril- 
los claros que ocupan la glandula digestiva de la cerata. Los cerata son cortos y 
redondeados. Los dientes radulares uniseriados tienen de 4 a 7 denticulos largos en 
cada lado de la ancha cuspide central. El pene esta armado con un estilete corto 
cuticular. 
Keywords: Nudibranchs, gastropods, Panamic, new species, biodiversity, Gulf of Cali¬ 
fornia 
The heterobranch sea slug fauna of the Pacific coast of Mexico has received considerable 
attention in recent years and many new taxa have been described (Gosliner and Bertsch, 2004; 
Bertsch, Valdes and Gosliner, 2009; Angulo-Campillo and Bertsch, 2013; Carmona, Pola, Goslin¬ 
er and Cervera, 2014; Pola, Sanchez-Benitez, and Ramiro, 2014; Hoover, Lindsay, Goddard and 
Valdes, 2015), but many new species still remain undescribed (Behrens and Hermosillo, 2005; 
Camacho-Garcia, Gosliner and Valdes, 2005). 
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