KEPOET ON THE TETEACTINELLIDA. 
423 
Remarks. — This sponge closely resembles Placortis simplex, F. E. Schulze, from 
which it differs by the larger size of the mieroxea and the smaller size and greater 
number of the actines of the aster. If we suppose the triod of Placortis to develop 
fresh actines, becoming smaller in the process, and the mieroxea to lengthen and to acquire 
a more constant and regular fusiform outline, we shall arrive directly at Astropeplus. 
The spicules of the Calthropella simplex on which the sponge is seated, occur 
mixed along with those proper to it, so that mingled with the asters in the ectosome 
of Astropeplus we find the characteristic spheraster of the Calthropella. This furnishes 
another indication of the extrusion of spicules from a sponge during life. 
Group II. HETEKOSCLEEA. 
Spintharophora in which megascleres are always present, and sometimes microscleres 
in addition. 
Demus I. Centeospinthaea. 
Heterosclera in which the microsclere when present is a euaster. 
Family 1. AxiNELLii>iE(0, Schmidt). 
Centrospinthara in which the ectosome is not a cortex, the mesoderm of the choano- 
some is collenchymatous, the chamber-system is eurypylous. The skeleton consists of axial 
fibres, and radial fibres proceeding from them to the surface. The megascleres are styles 
and rhabdi, which may be isoactinate or anisoactinate, or both. The' microsclere when 
present is a spheraster or strongylaster or oxyaster, and in one genus, Tricentrium, some- 
times a microcalthrops. 
Genus 10. Epallax. 
The choanosome is a regularly folded plate, the sinuses of the folds on one face are the 
main excurrent canals, on the other face the main incurrent canals. The spicules are large 
oxeas and asters, the former partly arranged in longitudinal fibres cemented by spongin. 
Epallax callocyathus, n. sp. (PI. X. figs. 1-12). 
Sponge (PL X. fig. 1), — Vasiform, expanding towards the margin, above which it is 
rounded and gently undulating, produced into a short, slender, strong stalk below, by 
which it is attached. Oscules small, opening into the interior of the cup in radiating linear 
series, those of adjacent rows irregularly alternating with each other. Pores in cribriform 
areas lying over the incurrent canals, which interdigitate with the excurrent canals, both 
crossing the walls of the sponge transversely in linear, longitudinal rows. 
