B. californica sensu-a-few-days-ago has been split, and WoRMS accepts it: http://www.marinespecies.org/aphia.php?p=taxdetails&id=1436161. The underlying paper is Ghanimi et al. (2020). Unfortunately, it is closed-access, but the authors have provided a copy that I've used to write up this split.

Relevant notes on distinguishing the two species from Ghanimi et al. (2020):

In addition to genetic differences, B. californica and B. chacei also exhibit consistent differences in size and in aspects of their external and internal morphology. Berthella chacei is typically smaller than B. californica. The largest specimen of B. californica examined anatomically in this study (34 mm long) was about 0.6 times as large as the largest specimen of B. chacei examined (20 mm long) and, as described in the Introduction, the two species are known to reach lengths of 127 mm and 70 mm, respectively. Berthella chacei has a white to creamy white mantle whereas B. californica has a creamy white to brown mantle. In B. chacei, the white dorsal spots on the mantle are on tubercles and the rest of the mantle is typically smooth, whereas in B. californica the white dorsal spots are not on the tubercles and the entire mantle is always smooth. The white dorsal spots on the mantle vary in size in B. chacei, but they are typically of uniform size in B. californica. White specks are present on the rhinophores, oral veil and the foot of B. chacei, whereas in B. californica typically no structure other than the mantle bears any white spots. Most specimens of B. californica possess a longitudinal white dorsal stripe on each rhinophore (Fig. 1A–C), a character not present in B. chacei (Fig. 1E–G). Finally, the egg mass of B. chacei (Fig. 1H) is white, wavy and relatively rigid, compared to the darker coloured, more delicate and less wavy egg mass of B. californica (Fig. 1C).

Here's a summary of what seem to be the differences that are relevant to making identifications on iNat (with help from Jeff Goddard):

	Berthella californica	Berthella chasei
Range	Ventura County, CA, USA to the Galapagos Islands, Ecuador	Sea of Japan to San Diego County, CA, USA
Morphology viisble in photos	Uniform dorsal spots No spots on the oral veil or rhinophores Rhinophores typically have a dorsal white stripe	Mixed-size dorsal spots Oral veil and rhinophores usually spotted Dorsal spots on tuburcles
Photos	Photo: Craig Hoover	Photo: Robin Agarwal
	Photo: Craig Hoover	Photo: Damon Tighe