Named by Carter.
Original description: Test cruciform with long rays terminated by long central spines. Rays uniform in width, of more or less equal length. Pore frames irregular in size, shape and arrangement; composed of thin bars with small rounded pores at vertices. Rays rectangular in cross-section. Central spines with three wide, rounded, longitudinal ridges alternating with wide, strong grooves.
Original remarks: This species differs from C. angulosa angulosa in always having much longer arms. Crucella angulosa Carter originally consisted of two distinctive morphotypes: one with short arms and one with much longer arms; these are now separated into subspecies.
Etymology: From the Latin: longus, -a, -um long, and brachium, i arm; longibrachiatus, -a,- um with long arms; adjective.