378 



in having the pores, in general, one-fourth smaller, and from C Anstedi 

 (ante, pp. 210, 337) in having them larger. 



The above figure, 352, is copied from Roemer, who gives it to illustrate 

 the internal structure of Astylof<pongia prceinorsa, a fossil sponge which 

 occurs in the Lower Silurian rocks of northern Europe, and also, accord- 

 ing to him, in rocks of the same age in Tennessee.* The structure of 

 the inner wall of the cup is very much the same in both of the species 

 above represented, but still I think they belong to different genera. In 

 our species the walls are as completely reticulated to the depth of six 

 lines, as in the inner surface of the cup itself. This is clearly shown by 

 the fragment above mentioned. Thei-e is a great difference also in the 

 general form of the two groups, the species of Oalathium being elongate- 

 turbinate like the corals Zaphrentis and Cyathophyllum, while those 

 figured by Dr. Roemer are more nearly globular. The genus Auloco- 

 pium, also illustrated by Roemer, has some turbinated species, but the 

 figures of the inside of the cup (of which several are given) do not show 

 any perforations : their absence, however, in the figures may be owing to 

 the imperfection of the specimens. 



Localitij and Formation. — Mingan Islands ; Chazy limestone. 



Collectors. — J. Richardson, Sir W. E. Logan. 



Genus Receptaculites, Defrance. 



Fig. 353. 



Fig. 353. — Diagram of the structure of Receptaculites, as it would be shown in a vertical 

 section through a sub-conical species, a, the aperture in the summit ; 

 b, the endorhin or inner integument lining the central cavity; c, the 

 ectorhin or external integument ; n, the usual position of the nucleus ; 

 V, the great internal cavity. The unshaded bands running from the 

 ectorhin to the endorhin represent the tubes. 



* Dr. Fehdinand Roembk, Die fossile Fauna der Silurischen Diluvial-Gcschiebe von 

 Sadexeitz bei Oels, in Niedei-Schlesien, p. 10, pi. II, fig. 6. 



