€ 110) 
carmata. And still, we want to designate them with a name; I 
propose to use for this the term microspira. 
5. Sterrospira. 
In the remarkable genus Placospongia the stony cortex and axis 
are almost entirely composed of spicula, which very strikingly resemble 
the sterrasters of Geodidae. Keller (1891la, p. 298) was the first 
to demonstrate that these spicula are of quite a different nature ; 
whereas the sterrasters develop from true asters, the cortical spicula 
of Placospongia take their origin from “Spirastern”. This observa- 
tion is confirmed by Lrenpenrecp (1894d, p. 115). Hanrrsen (1895, 
p. 214216) found the same for the corresponding spicula of Physca- 
phora (= Plancospongia) decorticans; as they possess in this species 
an elongated, somewhat crescent-shaped appearance Hanirscu called 
them ,selenasters”. In 1897 LENDENFELD, not acquainted with the 
paper of Hanirscu, proposed the name #pseudosterrasters” for the 
cortical and axial spicula of Plancospongia graeffei (= Physcaphora 
decorticans Han.). Uf one wishes to apply the rules of priority in this case, 
the spicula under consideration have to be called selenasters. I am, 
however, of opinion that these rules, excellent as they are for specific 
nomenclature, need not to be applied in other cases and I propose, 
therefore, the name sterrospira, which at the same time reminds us 
of the sterrasters (of the Geodidae) and the spiraxons. *) 
In the group of the fB-spirarvons the ideal axis of the spiculum is 
a line drawn on an elliptical eylinder. The simplest type of such 
a spiculum is 
1. Sigma. 
This term is introduced bij Ripiny & Denny (1887, pp. LXIII 
and 264) for spicula called by BoweRrBANK “bihamate’”’, “contort 
bihamate” and “reversed bihamate”. The authors say that the sigma 
consists of a “slender, cylindrical shaft, which is curved over so as 
to form a more or less sharp hook at each end. The two terminal 
-hooks may curve both in the same direction, when the spicule is 
said to be simple... or they may curve in different directions, when 
it is said to be contort... There is, however, no real distinction 
between the two, and, as a matter of fact, the spicules are nearly 
always contort to some extent”. Sorras (1888, pp. LXII) modified 
the definition into “a slender rod-like spicule curved in the form of 
the letter C. This spicule is not spiral though it probably arises 
1) For details I refer to a paper on Placospongia from Dr. Vernnovt and 
myself, to appear within a short time (Siboga-Expeditie. Monogr. VI. Porifera). 
8* 
