dredged up from the Gulf of Maaaar. S9 



Microcionina. 



I intended this family to include Dr. Bowerbank's genera 

 Microciona and Hymerhaphia (Brit. Spong. vol. i. pp. 188, 

 189), chiefly because they are all thin, flat, incr listing and 

 laminiform species, containing respectively a setaceous form of 

 spicule, and another more or less allied to the echinating one 

 of the Echinonemata. 



The distinguishing character between these two genera, 

 according to Dr. Bowerbank, is that the spicules of Microciona 

 are arranged in tufts or " columns " (ex. gr. M. atrosanguinea 

 = Scopalina, Sdt.), and those of Hymerhaphia are not. But 

 the spiculation is more persistent than the " columns " in many 

 instances, whereby the diagnosis would break down, as the 

 Microciona thus becomes a Hymerhaphia. Taking an oppo- 

 site view of the case, Hymerhaphia vermiculata, Bk., of course 

 contains no " columns ;" but H. vermiculata, var. erecta 

 ('Annals,' 1876, vol. xviii. p. 307, pi. xii. fig. 4 &c), does 

 (that is, " fasciculi "), with identical spiculation; so here the 

 diagnosis of Hymerhaphia breaks down. Again, Dr. Bower- 

 bank's Microciona camosa of 1866 is made identical with 

 Halichondria plumosa, Johnston, 1870 (B. S. vol. iii. p. 61), 

 and renamed Microciona plumosa. Now, considering that 

 Halichondria plumosa grows up into an erect massive form, 

 it must, according to Dr. Bowerbank's diagnosis, be a Micro- 

 ciona at one time, viz. when flat and incrusting, and at another 

 not — that is, when it is erect and massive ; hence I have pro- 

 posed a group " Plumohalichondrina " for this and similar 

 species, the most remarkable of which that I have seen comes 

 from Port Elizabeth, South Africa, where it appears to be very 

 abundant ; it is large, branched, and compressed, like an elk's 

 horn ; and they all possess the angulated (Bk.) equianchorate, 

 not the naviculiform spicule of Microciona. 



Nor is it uncommon to find an Echinonematous sponge 

 beginning in the flat form of a Microciona and then becoming 

 erect, as appears to be the case with Halichondria plumosa just 

 mentioned. But while this shows that the " columns " in 

 Microciona are not of much generic value, it also points out 

 that genera formed upon the characters of indigenous species 

 are very likely to break down when applied to world-wide 

 collections ; yet the same may be said of the latter until all 

 the species of a class are known. 



There is still another of Dr. Bowerbank's genera which, 

 both in spiculation and growth, is very nearly allied to these 

 thin, flat, incrusting laminiform sponges, viz. Hymedesmia ; 

 but here, again, his chief distinguishing character, viz. the 



