I moved the two female to the page. (Thanks to open a page for this species). I am sure they are S.lugubris.
I studied another 15 specimens from the same location and I read all what I can found on internet about (In English, Spanish, French and event I attempt to understand some in Latin).
The female after the last molt before to became adult and lay eggs change the color in black, black - olive and sometimes keep some dark brown (but seems that all become rather black in time).
Immature male and female have the same pattern. Mature male keep the pattern when become mature. In the adult females the pattern become barely visible or even at all.
On immature, on carapace is a urn shape (hence the name 'lugubris' if we think to the 'funerary urn' and maybe the black color of the females - I suppose). This urn shape it is still visible on mature female but sometimes can be difficult to discern, depend of light and angle.
A good image to show 'the urn'
First clue for ID was the way how I found them, in a pile of a palm dry leaves. This fact it is mentioned in Catalogue of Texas spiders (Dean 2016), quote: ' Habitat: (grass: grass); (orchard: grapefruit); (soil/woodland: debris under banana trees, palm tree, palm forest, under [bark, log])'. But I was able to find them only on debris under palm tree.
After I had some hypothesis, to check I attempted first to eliminate the other possible species found in Texas than I check again the information and description of species.
Until now, six species of Scytodes are recorded in Texas: S.atlacoya, S.dorothea, S. thoracica, S.lugubris, S.univittata and S.zapatana , but I considered S.fusca too due to the fact it is recorded in USA and it is a probability to be in Texas, too.
Most difficult - on one stage of knowledge or so, can be to eliminate the S.fusca.
The most enigmatic species I found to be Scytodes dorothea (Gertsch, 1935). I found very few information, about.
The urn shape on carapace seem to be a characteristic but the most fact what made me to be sure about the Id is the position and the shape of the 'ridges' on the female ventral abdomen.
The ridges:
Adult male ID by pedipalp is possible but seems to be more difficult. I was not able to take good pictures but as far I was able to see and interpret it seems to fit to ID.
Of course always it is a possibility to be wrong, but, at least, for now I am sure about ID. At least, because I had intention to contact an expert and even I tried to grow some spiderlings for more observations but a flood to the place where I worked force me to relocate and turned off my amateur research. So I lack a confirmation from an expert.
I will add more pics of others specimens.

Thanks for helping everyone with these tricky species IDs, including me!