PA]1E0MAN0X.— TEEArABICTYON. 93 



extending downwards from the summit of the cone. Circular canal-apertures, 

 1"25 mm. wide, are closely arranged in linear series in the channels, and also on 

 the summit. The canals appear to extend in a nearly straight direction to the 

 central portion of the sponge. The spicular nodes are about '16 mm. in thickness, 

 the arms about -lo mm. in length and -OJil mm. in thickness. The minute expanded 

 terminations at the ends of the arms are very clearly shown in microscopic sections 

 of this form. 



Nothing is known of the geological horizon or locality whence the specimen comes, 

 but the condition of preservation is precisely similar to that of specimens of Asti/lo- 

 spongia from the Silurian of North America. 



Genus PALEOMANON, Moemer, 1860. 



Pal^ojias^oij ceatera, Roemer. 



1848. Siphonia cratera, Roemer, Leonh. u. Bronn's Jahrb. p. 685, t. 9. f. 4, 4 a. 

 1860. Palaomanon cratera, Roemer, Silur. Faim. d. west. Tenn. p. 13, t. 1. f. 4, 4 a. 

 1877. Palaomanon cratera, Zitt. Studien, I Ab. p. 45. 



Distribution. Silurian (Niagara group) : West Tennessee. 



Family EURETIDM, Zittel. 

 Genus TEEMADICTYON, Zittel, 1877. 



TREiUDICTTOX EETICULATUM, GoldfuSS, sp. 



1833. Scyphia reticulata, Goldf. Petref. 1 Th. p. 11, t. 4. f. 1. 

 1833. Scyphia polyonunata, Goldf. Petref. 1 Th. p. 8, t. 2. f. 16. 

 1833. Scyphia fenestrata, Goldf. Petref. 1 Th. p. 7, t. 2. f. 15. 

 1833. Scyphia pertusa, Goldf. Petref. 1 Th. p. 6, t. 2. f. 8. 



1877. Tremadictyon reticulatum, Zitt. Studien, I Ab. p. 46 ; Neues Jahrbuch, p. 355, t. 2. 



f. 2, also p. 706; Handbuch d. Pal. p. 173, f. 89. 



1878. Spongites reticulatus, Quenst. Petref. Bd. 5, p. 28, 1. 115. f. 1-12, 14-23. 



Distribution. Upper Jura, Spongitenkalk : Heuberg, Randen, Nattheim, Streitberg. 



Tremadicttoiv obliquatum, Quenst. sp. 



1858. Spongites obliquatus, Quenst. Der Jura, p. 671, t. 81. f. 97. 

 1877. Tremadictyon obliquatum, Zitt. Studien, I Ab. p. 46. 



Distribution. Upper Jura : Heuberg, Randen, Wiirtemberg. 



