Vosmaeropsis mackinnoni is a species of calcareous sponge in the family Heteropiidae, and was first described in 1924 by Arthur Dendy and Leslie M.

4) colonial, consisting of a number of short, thick, subcylindrical individuals united together in an irregular manner along a greater or lesser portion of their length.

The individuals vary rather in size owing to their peculiar branching and colonial habit; an average full-grown person is 15 mm.

The skeleton of the gastral cortex consists exclusively of rather slender triradiates arranged tangentially, which become strongly sagittal (alate) towards the osculum, with the oral arms extended parallel with the margin of the latter.

The skeleton of the chamber layer consists of (1) the contripetally directed rays of the large subdermal pseudosagittal triradiates, (2) very large and stout subgastral sagittal triradiates, (3) similar triradiates whose paired rays lie at a variable distance beneath the gastral cortex, (4) the inner portions of the large oxea, whose outer portions project through the dermal cortex.

Fig.. 6 d); approximately regular, with conical, gradually tapering, sharply-pointed rays, measuring from about 0.23 by 0.026 to 0.4 by 0.04 mm.

6 e); approximately regular and more or less strongly sagittal; much smaller on the average than those of the dermal cortex, with slender, gradually tapering, sharply-pointedrays measuring about 0.21 by 0.013 mm.

(7) Oxea of the peristomial fringe; very long and slender, hair-like, usually broken off; measuring up to 2.3 by 0.009 mm.