78 Mr. G. R. Vine on Species of 



so. In examining a series of Cretaceous Polyzoa in the 

 possession of Miss E, C. Jelly, one specimen appeared to me 

 to belong to the genus. 



In describing an American Silurian form — in some respects 

 similar to forms found in the Wenlock Shales — Mr. E. O. 

 Ulrich ( Journ. of Cincinnati Soc. Nat. Hist. April 1879, pp. 18, 

 19) has established a genus under the name oi Rkopalonaria. 

 The species of the genus, B. venosa, Ulr., the author places with 

 the Crisiidffi, remarldng, " that the form has only been observed 

 incrusting Streptelasma corniculum. On account of the great 

 delicacy of the fossil, the fronds themselves are rarely found ; 

 but instead we find a series of impressions on the exterior 

 coat of the Streptelasma, which very well represents the fronds 

 and cells of the same." A specimen of the species described 

 by Mr. Ulrich is before me. It is from the same Cincinnati 

 rocks ; as I shall have to refer to the genus again, I have 

 thought that it might be more satisfactory to make reference to 

 an actual specimen than to the mere description of the same. 



ASCODICTYON, Nicholson & Etheridge, Jun. 



Ascodidyon, Nich. & Etli. jim., Ann. & Mag. Nat. Hist., June 1877, 

 pi. xix. ; " Notes on Polyzoa of tlie Wenlock Shales," Vine, Quart. 

 Journ. Geol. Soc. Feb. 1882, pp. 52, 68. 



1. Ascodictyon filiforme^ Vine. 



Ascodidyonjiliforme, Vine, " Notes on Polyzoa of the Wenlock Shales," 

 o/j. cit. pp. 54, .56 (merely referred to in the above). 



Organism filamentous, forming linear, contorted or clustered 

 threads, adherent to shells, stems of crinoids, fragments of 

 trilobites, but rarely to corals. Filamentous threads hollow, 

 but surrounded by delicate calcareous walls ; the hollows filled 

 with a dark brown granular mass. Lagena-Wko. divergences 

 developed on the sides of the thread, sometimes as single 

 vesicles, otherwise as groups of vesicles. Peculiarly clustered 

 stellate fibres are also formed at unequal distances. 



Locality. Buildwas beds, generally distributed throughout 

 the whole of the washings, but more abundant in nos. 36 

 and 38. 



This curious organism begins its existence as a mere speck 

 upon stone or shale or stem, which forms the nucleus of a 

 colony. From this delicate filaments are developed (fig. I. 1 a, 

 a^), sometimes in two or three, at other times in four different 

 directions ; these vary in thickness, but the average size, both 

 in breadth and depth, may be taken as measuring between 

 y^ and 2^0^ inch. The threads are sometimes, but rarely, 

 white, more generally of a dark brown tint. Viewed as 



