RADIATA. 



ECHINODERMATA. 



ASTEKOIDEA. 



Genus ASTERIAS, Linneus. 



ASTERIAS ? DUBITJM, ». sp. 

 Plate 3, fig. 3. 



Several impressious of a species of star-fish, apparently of the genus 

 Asterias, are present in the collection from a bed of light-red sandstone, 

 which occurs at a horizon of from 80 to 100 feet above the Triassic red 

 beds. 



The specimens are not in a condition to afford a full description of 

 their specific characters. They are of small size, the rays being from 

 three-fourths of an inch to one and one-fourth inches long, measuring 

 from the center of the body. The rays are slender and flexuous, most 

 of them being more or less curved in their direction and elevated along 

 the middle, as shown on a gutta-percha cast taken in a natural mold of 

 a group of three individuals. The upper surface is subangular, and In 

 structure they are apparently composed of small nodiform plates, placed 

 in longitudinal rows. The center of the body or disk is marked by an 

 obscurely pentangular depression on the upper surface. None of the 

 specimens show the under side of the body or rays, so that the charac- 

 ters of these parts are entirely unknown. 



The species appears to have been somewhat abundant, judging from 

 the condition in which they are grouped on the sandstone, and although 

 the specimens are obscure and too imperfect for positive determination 

 and description, it has been thought best to designate them by name, 

 as they will undoubtedly prove a characteristic form over a certain 

 region, and of a limited horizon. The sandstone is marked, on the 

 layers in which they are found, by ripple or wave marks, having a 

 width of about 3 inches, and indicates a near proximity to a shore-line 

 over the area where they were obtained, and that the individuals are 

 probably stranded specimens. A single very imperfect impression of a 

 Lamellibranchiate shell is represented on the same fragments of rock, 

 but too imperfect for determination. 



Formation and locality. — In red sandstones of Jurassic age, Park 



Sands, 70 feet above the red beds, on the east side of Spear-Fish Creek, 



near its junction with the Red Water, northeast of Crow Peak, Black 



Hills, Dakota. 



15 



