SHELL. Similar to M. brevispina s.s. but higher-spired, smaller (maximum length 60 mm), with seven teleoconch whorls. Protoconch similar to M. brevispina s.s. Spiral ornamentation stronger and sharper, than typical subspecies.
Axial ornamentation with more spinose varices, with short primary spines at shoulder, periphery, and base of body whorl. Alternating with primary spines, are slightly smaller secondary spines, occasionally including one on subsutural ramp. Siphonal canal usually with two equi-sized spines posteriorly, near base of body whorl.
Aperture with inner lip attached or only slightly raised above parietal area in contrast to wider, free inner lip of typical subspecies. Outer lip with weaker labral spine than typical subspecies.
Colour dark to pale purplish brown with axial ribs and most primary spiral lines yellow-brown to almost white. Darker olive-brown band below shoulder visible in some specimens.
Other features as in typical subspecies.
The shell of this subspecies may be distinguished from that of the typical form of M. brevispina by the presence of secondary spines, which are never seen even in the most spinose examples of the typical subspecies, or of M. brevispina senilis, and also by the smaller size, higher spire, and stronger spiral ornamentation. This geographic subspecies appears to be confined to Indonesia (including Borneo), but is apparently not common through most of this area. It appears to have been derived from M. brevispina macgillivrayi, which was present in the area it now occupies during the Pliocene and Plio-Pleistocene. It differs from that subspecies in having a paucispiral protoconch and in the development of secondary spines on the teleoconch.