Knowledge of the Spongida. 251 
are liable, like those of C. versatile and all other tetractinellids, 
to irregularity in the division of the arms; but when accom- 
panied by a particular form of flesh-spicule in great abun- 
dance, as in Samus anonymus and Samus (olim Pachastrella) 
parasiticus (No. 25, p. 410, pl. xv. fig. 41, a, 6, and No. 30, 
p- 60), 1 think that, however great the variety in the skeleton- 
spicule may be, the form of the flesh-spicule heve should 
decide the species question, as the branches in the skeleton- 
spicule are as inconstant as they are accidental. Schmidt’s 
second part of his descriptions of the sponges from the Gulf 
of Mexico, which were sent to him from America for this 
purpose (No. 31), reached me on the 2nd July 1880, just two 
months after my Report on the Manaar specimens (No. 30) 
had been written and illustrated; or I should have referred 
therein to his observations in connection with Corticium ver- 
satile and its relationship with Pachastrella, to which now I 
can only commend the student for instruction. . 
Sarcomella medusa, as 11s substance proclaims, is an Alge- 
rine specimen, shortly described by Schmidt as an irregularly 
convex body, medusa-like in consistence, and charged with 
one form of spicule only, viz. acerate, like a Reniera (No. 9, 
poll): 
Osculina polystomella, Sdt. Of this sponge, which came 
from La Calle, on the Algerine coast, and was forwarded in 
spirit to Schmidt by Lacaze-Duthiers, the former states in his 
description of it (No. 9, p. 3, Taf. 1) that its consistence is the 
same as that of Chondrilla, which, together with its being 
spiculiferous, is sufficient for our classification. It would have 
been more satisfactory if the thickness of the cortex had been 
mentioned in the text instead of having only been represented 
in the illustration with the indefinite term a little (geringe), 
when it may fairly be inferred to be very much, magnified. 
In 1870 I compared Osculina polystomella with Grayella 
cyathophora (No. 12, p. 73) from the Gulf of Suez, which in 
many particulars are very much alike—so much so indeed 
that I feel compelled now to add Grayella provisionally to the 
Gumminida as follows :— 
Grayella cyathophora was described and illustrated by my- 
self in 1869; and I still possess the little specimen in spirit as 
it came to me from the late Dr. J. H. Gray (No. 11, p. 189, 
pl. vil.). Since then a much larger but dry specimen has 
been added by purchase to the British Museum, which was 
stated by the dealer to have come from Port Elizabeth, Cape 
of Good Hope. It is 4x4 inches superficially, and half an 
