and Nomenclature of Sponges. 163 
families are determined by the presence or absence of certain 
_ kinds of spicules. ‘Thus, in the more inconspicuous siliceo- 
_ spicular Sponges, the presence of bianchorate or birotulate spi- 
cules characterizes Esperiade, and of stellate spicules Tethyadee 
both kinds are absent in Halichondriade. Now Dr. Bower- 
bank’s own specific descriptions show that some of his genera 
contain species belonging to two, and some to all of these three 
families ; yet he does not use the presence or absence of these. 
spicules to divide the genera into sections, though in his pre- 
liminary chapters he shows that he believes the stellate and 
bihamate spicules have an important use in the habits and 
economy of the animal. 
The following analyses of these genera show the details of 
this statement :— 7 
Almost all the Dictyocylindri belong to Halichondriade ; 
but D. fascicularis and D. stuposus have stellate spicules, and 
belong to Tethyade. 
_ Hymeraphia vermicularis and H. clavata belong to Hali- 
chondriade, and 7. verticillata and H. stellifera are 'Tethyade, 
having stellate spicules. 
_ The three species of Hymedesmia, for example, belong to 
three families—H. radiata to Halichondriade, H. stellata to 
Tethyade, and H. zetlandica to Esperiade. 
_ Six out of the eight species of Microciona have anchorate 
spicules and belong to Daanaie and the others, W. levis 
and fallax, to Halichondriade, having only fusiform spicules, 
Of the genus Hymeniacidon, which contains thirty-nine 
species, by far the greater part belong to Halichondriade, one 
to Clioniade; but there are scattered among them (why, I can- 
not comprehend) nine belonging to Esperiade, as (9) H. 
perarmatus, (15) H. variantia, (16) H. macilenta, (24) H.lingula, 
(25) H. floreum, (27) H. plumosa, (28) H. jecusculum, (33) H. 
subclavata, and (37) H. paupertas,—one, (39) H. Bucklandi, 
to Tethyade. : 
_ Of the twenty-eight species of Halichondria more than half 
do not belong to Halichondriade : thus (8) H. angulata is a 
_ Tethyad; (9) H. corrugata, (10) H. Thompsoni, (11) H. for- 
 _ etpis, (14) H. incrustans, (15) H. candida, (16) H. irregularis, 
(17) &. Dickiet, (18) H. Pattersoni, (19) H. pulchella, (20) H. 
Ingalli, (21) H. scandens, (22) H. Batet, (23) H. granulata, 
(24) H. Hyndmani, (25) H. nigricans, (26) H. albula, and 
(28) H. inornatus belong to Esperiade. 
. Isodictya is the great magazine genus of the work: it con- 
tains no less than forty-three species; about two-thirds of 
them belong to the family Halichondriade. 'The following— 
