304 
M. K. A. Zittel on Fossil Monactinellidce. 
Fig. 7. The same. Echinating spicule, more magnified (scale l-12th to 
l-1800th inch), a, echinating arm. 
Fig. 8. The same. Portion of surface of a “ column,” showing the spi¬ 
cules in situ. Diagram, much, but relatively, magnified, a, long 
setaceous acuate ; b, thick short acuate; c, undulating acuate ; 
d, echinating spicule. 
Fig. 9. Trikentrion lave, n. sp. Spiculation relatively magnified (scale 
l-24th to l-1800th inch), a, long setaceous acuate; b, short 
thick acerate ; c, fine acuate ; d, echinating triradiate spicule. 
Fig. 10. The same. Portion of fibre showing the spicules in situ. Dia¬ 
gram much, but relatively, magnified, a, long setaceous acuate; 
b , short, thick acerate ; c, fine acuate; d, echinating triradiate 
spicule. 
Fig. 11. The same. Different forms of acerate spicule, viz.:— a, bent; 
b, inflated in the centre ; c, acuate. 
Fig. 12. The same. Echinating spicule, more magnified (scale l-12th to 
l-1800th inch), a, normal form, triradiate ; b, occasional form, 
quadriradiate; c c, echinating arms. For comparison with 
figs. 7, 13 c, and 14, all of which are drawn on the same scale. 
Fig. 13. Trikentrion muricatum , Ehlers. Portion of fibre, showing the 
spicules in situ. Diagram, but relatively magnified (scale l-48th 
to l-1800th inch, the same scale as figs. 8 and 10, for comparison). 
a, acerate spicule; b, echinating triradiate spicule; c, the latter 
more magnified ; d, echinating arm. 
Fig. 14. Dictyocylindrus laciniatus , n. sp., and D. Pykii , n. sp. Echi¬ 
nating spicule. 
[To be continued.] 
XXXIV.— Studies on Fossil Sponges. —III., IV., V. Monacti¬ 
nellidce , Tetractinellidce , and Calcispongice. By Karl 
Alfred Zittel* *. 
III. Monactinellidce, Zittel. 
In my memoir u Zur Stammesgeschichte der Spongien ” f, 
I adopted the following orders of sponges, founded chiefly 
upon the grouping proposed by O. Schmidt (Atlant. Spong. 
p. 83), namely:—1. Myxospongise, Hack.; 2. Ceraospongise, 
Bronn ; 3. Monactinellidae, Zitt.; 4. Tetractinellidse, Marsh.; 
5. Lithistidte, O. Schmidt; 6. Hexatinellidte, O. Schmidt; 
7. Calcispongite, Blainv. 
To the Monactinellidse I refer all sponges the skeleton of 
which consists of uniaxial siliceous spicules. 
Of the numerous uniaxial siliceous spicules from Tertiary 
* Translated by W. S. Dallas, F.L.S., from the ‘ Abhandlungen der 
k. bayerischen Akademie derWissenschaften,’ II. Classe, Bd. xiii. pp. 93- 
138. 
t Festgabe der philosophischen Facultat zum 50-jahrigen Doctor- 
jubilaum des Professor von Siebold. Munich, 1878. 
