OF THE 



SILURIAN AND DEVONIAN ROCKS, 



COELENTERATA. 



SPONGIA. 

 Genus Brachiospongia. Marsh. 



Described by Marsh in Am. Journal of Scie. and Arts., 2d series. Vol. 44, 1807 Etymology: brachium, 



an arm; spongia a sponge. 



Brachiospongia digitata. OWEN 



Plate XXXV., figure 3, and Plate XXXVI., figures 1 and 3. 

 Scyphia digitata, Owen. First Ky. Geol. Kep., Vol. II., p. Ill 1857. 



This fossil is very peculiar and very interesting ; Prof. D. D. Owen, who 

 described it in his Kentucky Report, placed it in the genus Scyphia of 

 Schweigg, but its proper place is in the later established genus Brachiospongia 

 of Marsh. It consists of a circular or elliptical central body, which is hollow, 

 and has on its lower side an elliptical aperture occupying about one-third 

 of the lower surface. This aperture is surrounded by an elevated thick brim, 

 which rises in the specimen before me more than an inch and a quarter above 

 the general surface; its greater diameter measures four and its smaller two 

 inches and a quarter. From the circumference of the central body radiate in 

 my shell twelve large, cylindrical, geniculated tubes, while in fossils seen by 

 Prof. Owen he counted only from eight to eleven. These tubes start from the 

 periphery with a downward direction for about a little more than an inch, 

 where they make an abrupt turn of about ninety degrees upwards, to the ex- 

 tent of more than three inches. If the interspaces between the tubes were 

 closed, the fossil would form a medium sized basin or bowl, with an elevated 

 center. The tubes are all of about the same size and shape ; all have an aper- 

 ture on top, which is different in shape ; in some the opening is elliptical, while 

 in others, it extends to the knee ; but there is no doubt that, in original speci- 

 mens, the aperture was limited to the top, and the lateral enlargement of the 



