M. K. A. Zittel on Fossil Calcispongice. 121 



Skeletal fibres rather coarse, chiefly consisting of simple 

 bacillar spicules, among which, however, there are some scat- 

 tered large triradiates. 



The development of the canal-system forms the essential 

 character of this genus, and distinguishes it very definitely 

 from Peronella, with which it most nearly agrees externally. 

 The coarse radial canals of the stomachal cavity are always 

 present ; but, on the contrary, the incurrent tubules may some- 

 times become very fine, or, under circumstances, entirely dis- 

 appear. In the latter case, of course, the ostia of the surface 

 are absent. The constitution of these afferent canals varies 

 extraordinarily according to the species ; in general they are 

 most strongly developed in the Triassic and Middle-Jurassic 

 species. 



The stomachal cavity is also very variable. Sometimes it 

 becomes nearly tubular, as in Peronella, and reaches almost to 

 the base, but then always shows large canal-ostia ; sometimes 

 it forms only a shallow funnel, from which issues a bundle of 

 vertical and curvilinearly diverging coarse canals. 



In spite of these differences, which strike even the passing 

 observer, with respect to the constitution of the stomachal 

 cavity and canal-system, the transition between the two ex- 

 tremes may be so completely demonstrated, that I have been 

 unable to determine to divide this series of forms into several 

 generic groups. 



Fromentel, partly upon unimportant characters (occurrence 

 as single persons or in composite stocks, presence or absence 

 of an epitheca), and partly upon erroneous observations, has 

 established a whole series of genera, which, in my opinion, 

 are untenable. 



The canal-system of Eudea, Diseudea, and Polycnemtseudea, 

 From., is decidedly incorrectly described, inasmuch as the 

 canals never pierce the wall. In Monotheles and Distheles the 

 stomachal cavity is not, as described by Fromentel, shallow 

 and superficial, but even in Monotheles stellata itself consider- 

 ably impressed, funnel-shaped, and divided into vertical tubes 

 at its lower extremity. A weak epitheca occurs at the base 

 of several species ; others, however, are quite naked. 



The genus Corynella is distributed from the Trias up to 

 the uppermost Cretaceous. As typical species may be men- 

 tioned : — 



a. From the Trias. 



1. Myrmecium gracile, Munst. Beitr. iv. Taf. i. figs. 26, 



2. Cnemidium pyriformc, Klipst. Bekr. Taf. xx. fig. 5. 



