Distrito Federal, Mexico Civil Record translation

Happy Holidays to all:

I have a civil marriage record from Distrito Federal, Mexico dated 07 Jan 1917 and I am unable to translate two statements. “En la casa no 94 de la oclava del Reloj el Sr Pbro D.J. Guadalupe Chavez, V.P. asistio a siete de enero de mil novecientos diecisiete al matrimonio que in extremis (or fue in extremis) contrajeron Juan Breña y Ma Gonzalez fueron testigos Francisco y Ana Breña “

I am having trouble finding "oclave del Reloj" on any map. Does anyone have a historical map of DF. Quite possible this was located behind la Cathedral in front of Teatro Alarcon (or so I was told).

Also what does que in extremis or fue in extremis means.

And while on the subject of maps, I am looking for Callejon del Indio Triste No 59, Zacatecas, Zac, Mx which was the residence of my uncle, Marcelo Gonzalez.

Any assisstance is appreciated. Anita