GENERA, SPECIES, &C. 
Spong. 15 
large nuclei, which embrace the spicules ; here occur also the ova, found 
in special brood-chambers when large, at which time they are rich in 
yelk-granules. Sexes apparently distinct. The hamate spicules are 
developed around nuclei ; no cell-wall observed. From their position, 
and the characters of their parent cells, the cortical acerates appear homo- 
logous with the globates of Geodina. The elongate spicules remain long 
enclosed in their parent cells. The subdermal and flagellated chambers 
and the mark are developed early, the fibrous layers late. A com- 
parison with Rhaphidotheca show's that Tetilla forms the transition from 
Monactinellida to Tetractinellida. 
Tethya cranium. Norman, (1) pp. 39-43, recognizes 5 distinct varieties 
of this species as met with in British and outlying Scottish waters, 
stating at the same time his opinion that they may prove to be of specific 
rank : viz., var. 1, typica ; 2, zetlandica , Carter ; 3, acufera , nov. ; 4, abys- 
sorum , Carter; 5, infrequens , Carter. 
Sielletta aspera, Carter, (1) p. 30, — Ecionemia ponderosa, Bk., accord- 
ing to Norman. 
Pachymatisma johnstonia, (15) pi. vi. = Caminus osculosus , Grube. 
The histology, canal system, and spicules described by Sollas. The 
bacilli are homologous with the dermal stellates of Geodia. The oscular 
opening in this form is to be regarded as due to the excessive develop- 
ment of a single exhalant chone, whereas Cydonium is lipostomous, 
aud hops has a number of openings corresponding to as many chones, 
and Geodia has a single opening due to the union of several 
chones ; each (original) exhalant chone representing au individual. The 
pores are constant and confined to certain areas. The chones agree 
generally with those of Geodia barretti in form and minute structure. 
The main exhalant tubes open into a large chamber, which leads by a 
sphinctrated opening into a terminal tube, the substratum of whose 
walls consists of vacuolated tissue ; the sphincter is very thick, and has a 
complicated structure. 
Geodia barretti , Bowerbank, (17) p. 23, pis. iii. figs. 50 & 51, iv. 
figs. 120-122, from near Hammerfest, described. A system of crypts 
observed between the exhalant chones and canals. 
Geodia gibberosa , (2) p. 363, pi. xii. fig. 31 ; probably includes G. 
caribbcea , Duch. & Mich., tumulosa and tuberculosa, Bowerbank. 
Geodia gigas may attain a diameter of some feet; GraefEe, (7). 
Placospongia melobesioides, (2) p. 357, pi. xii. fig. 33. A group Placo- 
spongina , proposed by Carter, to include this form. 
CALCAEEA. 
Lcucaltis solida. Vosmaer finds, (1G) p. 5, that the canal systom belongs 
to the same type as Leucandra aspera ; ho has experimented upon it in 
the living state with carmine. 
Sycandra ciliata, a form mentioned by G. C. J. Yosmaer, Tijdschr. 
Nederl. Dierk. Yer. vi. p. Iii., as transitional var. coronata, from Bergen- 
op-Zoom, reaching the size of 80 mm., and possibly uniting the species 
with S. coronata ; the specimens all hung mouth downwards. 
