There is a lot that still needs to be explained about Batrachoseps south of the LA basin. The most recent treatment (Martinez-Solano et al. 2012, Molecular Phylogenetics and Evolution) shows a significant genetic gap between northern and southern populations now assigned to B. major, certainly a species-level difference, with the contact running SW-NE across northern San Diego County, with the closest approach between the two being in Ramona. The southern animal is smaller and darker, sometimes almost black (and black-bellied), and I sorta suspect the animals reported here are southern major rather than B. nigriventris, based on short(er) tail length, large(r) feet, and wide(r) heads. The northern part of the B. major range map from the 2012 paper is copied here (unfortunately it does not show records for B. nigrventris).

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Guys like Fundad who know all the micropatches of habitat remaining in the LA basin proper really need to help the Berkeley crowd out with sampling localities, eh? Soon they truly will be gone from LA, and nobody will know what genetic information has been lost.
Anyone who would like an e-copy of the Martinez-Solano et al. paper can PM me (but include your e-mail!) -- one of the hot issues would be to find northern and southern major in sympatry, and the other is to clarify the southern end of the range of B. nigriventris, preferably by finding them together with southern B. major. Without doing the genetics, sympatry with some subtle but consistent differences in morphology is going to be what carries the day here.
More complications, the southern unit of B. major consists of 5 species-level entities (only one in the US). The Los Coronados Islands and San Diego animals were named as Batrachoseps leucopus by E.R. Dunn in 1922, and the dark San Diego animals have long been informally called B. major minor as a joke (not to be confused with B. minor of SLO County). However, the Coronados populations group with northern, not southern B. major, so B. leucopus would be a synonym of B. major Camp 1915, and not a name available for the San Diego or Baja populations. Helping even further to keep it real, there are two species of B. nigriventris, and it is the southern, as yet unnamed, species we are talking about here. So ALL the names we are using tonight are
wrong and will be changed, yahoo for taxonomy.
My best guess is that those animals are southern B. major, but I would strongly encourage you to work out radially from that site and see if you can discover a place where the two species co-occur. And thank you for taking enough photos that actually show things like feet and bellies clearly!