SPONGES, GRATOLITES, CORALS. 59 



Receptarulitfs oweni.] 



are indicated by furrows left between the casts now filling the original spaces. 

 Between the four principal canals, which seem to have communicated with four 

 circular hollows, one- situated at each angle of the rhombic spaces, are two other 

 canals, and these also seem to have had openings in the upper surface. In other 

 words, each plate had originally twelve small semicircular hollows communicating 

 with twelve horizontal canals joining in the center with the vertical ray. Where 

 the filling of the spaces between the canals is not preserved, tubercles can be seen 

 distinctly situated at each angle of the rhombic depressions, with two, and occa- 

 sionally only one pustule between them. Along their edges the plates are separated 

 from adjoining ones by distinct walls. These walls are not a portion of the skeleton, 

 but are foreign matter which has accumulated between the plates, and has more or 

 less disturbed their natural position. 



This species is known throughout the Northwest as the "sunflower coral," "lead 

 fossil," or Eeceptaculites oweni Hall. The specimens from Minnesota are from lime- 

 stone and calcareous mud-stones, and rarely occur as hollow casts, but commonly as 

 impressions of the skeleton. The vertical rays are filled usually with crystalline 

 calcite. 



Dr. Hinde, in treating of R. occidentalis Salter, and R. oweni Hall, says: "The 

 examples from Illinois and other western states are usually of somewhat greater 

 diameter than those from the same horizon in Canada, but from a comparison 

 of specimens from these different places I am unable to detect any differences which 

 would justify regarding them as distinct species. Their external aspect is, however, 

 strikingly dissimilar owing to their different states of fossilization" (loc. cit. p. 843). 

 On account of the greater size attained by R. oweni, and the plates of the inner sur- 

 face having twelve canals instead of four, as in R. occidentalis, a central knob on each 

 head-plate of the spicules on the outer surface of the former, should be sufficient to 

 distinguish this species. 



Frii-mation and locality. Throughout the Galena of Minnesota, Wisconsin, Iowa and Illinois. Some 

 of the more prominent localities are : six miles south of Cannon Falls, Kenyon, Mineola, Fountain, near 

 Marion, Wasioja, and Stewartsville, Minnesota; Decorah and Dubuque, Iowa; Green Bay, Wisconsin ; 

 Galena and Dixon, Illinois. 



Collectors. Miss Cora E. Goode, W. H. Scofleld, and the writers. 

 Mus. Beg. Nos. 3375, 4944, 6758, 7251, 7714-7721. 



SYNOPSIS OF AMERICAN -SPECIES OF RECEPTACULITES. 



K. ARCTICUS Etherldge. 



1878. lieceptiii-iiliii-x urdicus ETHKKIDGE. Quart. Jour. Geol. Soc. London, vol. xxiv, p. 576. 

 1882. K&xptaculites arcticus JONES. Catalogue Foss. Foraru. British Museum, p. 3. 

 1884. Jteceptaculiles arcticus HINDE. Quart. Jour. Geol. Soc. London, vol. xl, p. 845. 



Formation and locality. Lower Silurian : Cape Louis Napoleon and Cape Primer. Arctic regions. 



