114 THE PALEONTOLOGY OF MINNESOTA 



[Rhopalonaria, Vinella. 



other eighteen. In the absence of good examples of the English Wenlock species, 

 Vinella radiciformis Vine, sp., which these specimens must greatly resemble, I propose 

 to designate the American form provisionally as vir. oonferta, in allusion to the 

 unusually close development of the nuclei. 



The inclusion of all the paleozoic Ctenostomata. in one family, the Ascodidyonidce, 

 (see Geol. Sur. Ill,, vol. viii, p. 335) is likewise only a provisional arrangement. 

 Indeed, I am satisfied that Rhopalonaria, Ulrich, at least, which is evidently related 

 to the recent Arachnidium, Hincks, belongs to a distinct family. 



Figure 8e is taken from the best example of Rhopalonaria venosa Ulrich, now at 

 hand.* This species, so far as known, is restricted to the upper beds of the Hudson 

 River group, and the specimen now illustrated is from those beds at Waynesyille, 

 Ohio. Usually nothing remains to attest the former presence of this brypzoan, 

 except a series of shallow excavations in the substance of the body upon which it 

 grew. These excavations, however, correspond very well with the form,- or rather, 

 the outline of the cells and extremely delicate connecting stolons of the zoarium it- 

 self. The latter must have been quite liable to destruction during the process 

 of fossilization, and, though diligently searched for, not a single example, so far as I 

 am aware, has yet been found in which it is preserved in even a fairly satisfactory 

 manner. In the best specimens the stolons are clear enough, but the swollen por- 

 tion of the zooecia' is always more or less obscure. Now and then, it is true, some 

 evidence is presented to show that the orifice was situated near one end in the center 

 of a slightly elevated portion of the surface. These facts, though unfortunate, tend 

 nevertheless to establish the ctenostomatous affinities of the fossil. If, as already 

 intimated, Rhopalonaria is related to Arachnidium, then perfect zoarial preservation 

 is>not to be expected. On the contrary, if such a condition were common, as in cal- 

 careous zoaria, the relationship might well be doubted, Since the almost membran- 

 aceous zoariunj of Arachnidium and many other Ctenostomata, is, perhaps, quite 

 incapable of preservation in a fossilized state. 



Vinella repens TJlrich. 



PLATE I, FIGS. 1-5. 



Vinella repens Ulrich, 1890. Jour. Cin. Soe. Nat. Hist., vol. xii, p. 174. 



Original description.— " Zoarmm repent, the stolons delicate, thread-like, often 



longitudinally striate, straight or flexuous ; from 0.06 to 0.11 mm. 'in diameter; 



bifurcating often and sometimes arranged in a radial manner about a central node. 



- Where best preserved, very small pores arranged uniserially along the center of the 



*The original type of the genus and species has heen mislaid or lost. 



