146 GEOLOGY AND PALEONTOLOGY. 



The specimens present some variety in the greater or less elevation of the apex ; the hase is 

 often convex near the margin, becoming gradually depressed towards the centre. The tuhercles 

 are very minute above, giving a sense of roughness to the touch, becoming larger on the sides 

 and much larger below. The upper surface is often nearly smooth, while the lower surface 

 retains the tubercles strongly preserved. 



Fig. 4(1. Profile view. 



Fig. ib. Upper surface. 



Fig. 4c. View of the base. 



Fig. 4e. Ambulacral and interambulacral spaces enlarged. 



Fig. if., g- Enlargement of a tubercle of base. 



TOXASTER ELEGANS. 



Plate XXI, Fig. 1 a-e. 



Hemiaster elegans, Shumard, in Marcy's report of Exploration of the Eed Eiver of Louisiana; 



page 210, pi. 2, fig 4 a, h, c. 



Shell subcordate-ovate, much elevated, apex anteriorly sub-central, rotund before, and 

 emarginate in the middle by a sinus which terminates below in the mouth ; obtuse or subtrun- 

 cate behind, with a shallow depression below the vent ; mouth transverse, round-oval, with a 

 shallow depression on each side extending to the margin, anus oval, near the upper margin ; the 

 larger tubercles scattered upon the upper surface, and becoming more numerous and larger on 

 the sides and lower margin ; a triangular lanceolate sj^ace beginning near the mouth, and 

 widening to the posterior extremity, covered with large tubercles, with a space on each side 

 entirely smooth, or with a few scattered tubercles. 



This species has the ambulacral areas defined by broad, shallow grooves, which, with the 

 exception of the anterior one, extend to the upper outer margin of the test. It resembles in 

 many of its characters the specimens which have been identified as Toxaster Texanum, but the 

 apex is more nearly central (being anterior to the centre, while in that one it is posterior.) In 

 the specimens under consideration, the ambulacral spaces are all deeply impressed, and the 

 antero-lateral ones are more divergent ; the anus is nearer tbe upper edge, and its greatest 

 length is in a vertical direction. Although the figures of Dr. Shumard convey no very definite 

 idea of the characters, yet his description is very satisfactory, and leaves little doubt regarding 

 the identity of that species with the one under examination. 



Fig. la. Upper side. 



Fig. IZ*. Lower side. 



Fig. Ic. Profile of posterior end. 



Fig. Id. Lateral view in outline. 



Fig. le. Enlargment of the surface. 



Locality. — Eagle Spring, Texas. 



