56 THE PALEONTOLOGY OF MINNESOTA. 



[Reoeptaenlites. 



figure by which it is adapted to fit in with the adjoining spicular plates to form an 

 exterior layer to the organism. Strong confirmatory evidence of the theory that 

 the summit plates of the spicules are modifications of the sixth ray in the ordinary 

 hexactinellid spicule, is afforded by the small blunted knob which projects in the 

 center of these summit plates in the best preserved examples of Sphairospongia, 

 and traces of which are also present in Acanthoconia . In these forms we find the 

 commencement of the sixth or summit ray in the small central knob, from which, 

 as a centre, the plate is developed horizontally by successive marginal additions." 



A new species of Receptaculites, seen in the collection of Mr. E. 0. Ulrich, from 

 the Lower Silurian near Knoxville, Tennessee, has the vertical ray of the spicules 

 with two constrictions, one immediately below the head-plates, and the other near 

 the center of their length. 



RECEPTACULITES, Defrance. 



PLATE F, FIGS. 1-4. 



1827. Beceptaculites, DEFRANCE. Dictionnaire des Sciences Naturelles, t. 45, p. 5, atlas, pi. 68. 



1859. Receptaculites, SALTER. Canadian Organic Remains, dec. i, p. 43. 



1860. Beceptaculites, EicnwALD. Lethaea Rossica, p. 427. 



1863. Beceptaculites, HALL. Sixteenth Rep. N. Y. State Cab. Nat. Hist., p. 68. 



1865. Beceptaculites, (partim) BILLINGS. Paleozoic Fossils, vol. i, p. 378. 



1865. Beceptaculites, (partim) BILLINGS. Canadian Naturalist and Geologist, sec. ser., vol. ii, p. 184. 



1868. Beceptaculites, DAMES. Zeitschr. der deutschen geol. Gesellschaft, bd. xx, p. 483. 



1875. Beceptaculites, GUMBEL. Abhandl. der k. bayer. Akad. der Wissensch. bd. xii, p. 170. 



1876. Beceptaculites, ZITTEL. Handbuch der Palaxmtologie, pp. 83. 727. 

 1880. Beceptaculites, ROMER. Lethasa Palfeozoica, p. 285. 



1884. Beceptaculites, HINDE. Quart. Jour. Geol. Soc. London, vol. xl, p. 821. 



1885. Beceptaculites, JAMES. Jour. Cincinnati Soc. Nat. Hist. vol. viii, p. 163. 



1889. Beceptaculites, NICHOLSON. Manual of Palasontology, vol. i, p. 170, tigs. 61a-61d ; vol. ii, p. 1563. 

 1891. Beceptaculites, JAMES. Jour. Cincinnati Soc. Nat. Hist., vol. xiv, p. 60. 



Description." Cup or platter shaped bodies of considerable size, with walls of 

 definitely arranged spicules. The outer surface is formed by the rhomboidal head- 

 plates of the spicules ; beneath these are the horizontal rays and robust subcylin- 

 drical vertical rays, which are connected with an inner layer or perforated plate. 

 Communication with the exterior was carried on between the margins of the sum- 

 mit-plates of the spicules on the outer surface, and through the cylindrical canals of 

 the inner surface layer, or, according to Gfimbel, through intermarginal canals." 

 (Hinde, loc. cit.) 



According to Nicholson, Rauff concludes that " the Receptaculitidce are spherical 

 or pyriform bodies, with a central closed cavity, the supposed basin-shaped examples 

 being only fragments of the base." Receptaculites oweni Hall, is a platter-shaped 

 species attaining a great diameter ; is widely distributed, and of common occur- 

 rence in the Galena formation throughout the Northwest. In Minnesota, the 



