W. A. Parks — Parasite from the Devonian Pocks. 135 



Art. XVII. — A Remarkable Parasite from the Devonian 

 Rocks of the Hudson Bay Slope • by W. A. Parks. 



It was the writer's privilege, during the summer of 1903, to 

 be engaged on certain geological investigations in the basin of 

 the Moose river, and the opportunity was afforded to do a 

 small amount of collecting from the Devonian area surround- 

 ing the southern end of James Bay. This examination was 

 conducted, more particularly, on the Kwataboahegan river, a 

 stream entering the Moose about 12 miles above Moose Fac- 

 tory, which is situated near the mouth of the great river. An 

 account of the fauna of the Lower Devonian rocks there 

 exposed will appear in the Report of the Bureau of Mines 

 of Ontario for the year 1904. In addition to some new spe- 

 cies, described in the article referred to, the attention of the 

 writer was drawn to what appeared to be a new species of 

 Platyostoma with a*remarkable surface ornamentation. This 

 fossil, which occurs abundantly, has the shape and general 

 appearance of Platyostoma lineata, but the surface differs from 

 that species by the possession of a peculiar reticulated orna- 

 mentation. 



In nearly all cases, casts only of the numerous gasteropods 

 characteristic of the series are found ; only one Platyostoma 

 was collected retaining any trace of the shell which shows the 

 ordinary fine lines presented by P. lineata. Among the great 

 number of external casts of this species many were seen to pre- 

 sent a constant reticulated appearance, as if the outer orna- 

 mented part of the shell had been preserved after the inner 

 layer had been dissolved. Such was the conclusion arrived at 

 in the field ; but microscopic examination in the laboratory 

 renders this conclusion very improbable. Many of these ex- 

 ternal casts show the impression of the lines of growth charac- 

 teristic of the exterior of P. lineata, proving that the structure 

 observed is something entirely external to the shell of the gas- 

 teropod, and therefore to be regarded as of a parasitic nature. 

 This parasite is most intimately associated with the shell pene- 

 trating into the umbilicus and into the deepest parts of the su- 

 tures. This fact makes it very difficult to decide that we are 

 not dealing with an external layer as first suggested. 



The lower or basal aspect of the parasite is well seen on the 

 casts of the exterior of the Platyostoma. The outer surface 

 was not observed, as the organism is so persistently imbedded 

 in the matrix as to render all attempts to free it abortive. 



At least two species of this creature occur, differing in the 

 size of the elements composing them and in some minor points 



