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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 64, No. 6 
cylindrical, slightly shorter than the narrower oral tentacles. The cerata are short and rounded with 
an acute apex where the cnidosac is located. They project outwards randomly, cover most of the 
notum, and are arranged in numerous linear rows. There are 3 rows in the precardiac ceratal rows. 
In four specimens, the three precardiac rows, beginning with the most anterior row, contain 1^4, 
2^4, 3^4, cerata per row. After the interhepatic space, there are four postcardiac ceratal rows, each 
of which contains 1^4 cerata. The anus is acleioproctic, situated dorsally at the base of the upper 
ceras of the first postcardiac ceratal row. The genital opening is ventral to the first and second pre¬ 
cardiac ceratal rows. 
Buccal armature: The jaws are thin and elongate (Fig. 6A) with a long inner margin. The mas¬ 
ticatory border of the jaw contains 31 simple acutely-pointed triangular denticles (Fig. 6C). The 
radular formula is 36 x 0.1.0 in the paratype specimen CASIZ . The central cusp is much wider and 
longer than the adjacent lateral denticles. There are 4-7 primary lateral cusps on either side of the 
wider central cusp (Figs. 6B, D, E) Secondary denticles between the primary lateral cusps are 
absent, although some denticles are shorter and narrower than the ones on either side of them. 
Reproductive system: The reproductive system is androdiaulic (Fig. 4B). The ovotestis folli¬ 
cles contain a large female acinus surrounded by a series of smaller male acini. The ampulla is large 
and saccate and divides distally into the short oviduct and vas deferens that appears to have a glan¬ 
dular texture. The prostatic portion of the vas deferens is thin and narrows into a short, convoluted 
ejaculatory duct that joins the penis near the junction of the penial gland with the penial papilla. 
The penial gland is pyriform and curved, whereas the penial papilla is sausage-shaped, with a short, 
straight, cuticular penial stylet (Figs. 6F, G). The female glands are well-developed and small albu¬ 
men and membrane glands are clearly visible, as is the larger mucous gland. A spherical bursa cop- 
ulatrix is present at the distal end of the reproductive system and connects to the gonopore via a 
narrow elongate duct. 
Remarks. — Despite the lack of suitably preserved specimens of this species for molecular 
study, the presence of morphological features strongly suggest that it is correctly placed in the 
genus Tenellia. In the recent revision of Fionidae, Celia et al. (2016), characterized Tenellia as 
including most members of the Fionidae having numerous well-separated ceratal rows with more 
than a single ceras per row. This is certainly the case in T. ivetteae. While it appears that not all 
species of Tenellia possess a penis armed with a straight penial stylet, the majority of species have 
this anatomical specialization, including T. ivetteae. Until fresh material is available to confirm the 
phylogenetic relationships and systematic status of T. ivetteae, we tentatively place it in Tenellia, 
based on the morphological attributes described above. 
Tenellia ivetteae differs from all species of Fionidae previously documented from the temper¬ 
ate and tropical eastern Pacific. It is one of a handful of species that have whitish pigment as the 
predominant body color. Only T. albocrusta (MacFarland, 1966) and T. riosi (Hermosillo and 
Valdes, 2008) comb nov., have a similar external appearance. Tenellia albocrusta is found the east¬ 
ern Pacific from Alaska to La Paz, in the Gulf of California (Berhens and Hermosillo, 2005). In 
this species, the body is covered by irregular patches of opaque white and encrustaceans of opaque 
white on the cerata. In T. ivetteae, the opaque white is found only on the outer portions of the 
rhinophores and oral tentacles. The digestive gland within the cerata in T. albocrusta is green to 
brown whereas it is pale yellow in T. ivetteae. Tenellia riosi is known from only from the Bahia 
Banderas region of Mexico. As in T. albocrusta, T. riosi has opaque white patches on the notum 
that are absent in T. ivetteae. It also has a black digestive gland basally in the cerata and salmon 
pink gland more distally. The shape of the radular teeth differs in the three species. In T. ivetteae, 
the central cusp of the tooth is longer than the adjacent denticles, whereas it is much shorter than 
the adjacent denticles in T. albocrusta (MacFarland, 1966, pi. 67, figs. 13, 14) and slightly shorter 
