50 BULLETIN 115, UNITED STATES NATIONAL MUSEUM. 



These numbers bear no relation to any other characters, but it 

 will be noted that 90 per cent of the specimens have 15 arms or more, 

 and 60 per cent of them have 15 with only one or two arms more or 

 less; so the type for this form is 15 arms, with a tendency to increase 

 toward 20. The grouping of the species hereunder is more or less 

 artificial, and the definitions are lacking in decisive characters, de- 

 pending altogether upon the surface markings. 



DOLATOCRINUS VENUSTUS MUler and Gurley. 



Plate 13, figs. 1-5; plate 15, fig. 8. 



Dolatocrinus venustus Miller and Gurley, Bull. 4, 111. St. Mus., 1894, p. 23, 



pi. 2, figs. 16-18.— Rowley in Greene, 1903, p. 160, pi. 47, figs. 9, 10. 

 Dolatocrinus aureatus Miller and Gurley, Bull. 4, 1894, ]>. 24, pi. 3, figs. 1-3. 

 Dolatocrinus lyoni Miller and Gurley, Bull. 9, 1896, p. 44, pi. 3, figs. 4-6. 

 Dniatocrinus corh^diferus Rowley, 1903, p. 151, pi. 44, fiG:s. 13-15. 



Interrupted 'ridges, coarse nodes or pustules. These surface 

 characters are not so well shown by the original figures as by the new 

 drawings here given, made upon a photographic basis directly from 

 the type. More faulty still are the authors' figures of venustus in 

 not showing the general hemispheric contour, which is missed com- 

 pletely in their side view (fig. 17). The description agrees with the 

 type as it is designated in the Gurley collection. Some other speci- 

 mens among the duplicates labeled with this name are of doubtful 

 authenticity, but I have four good specimens that can be assigned to 

 this species, including a very characteristic one from Michigan. 

 The species attains a larger size than the other two, ranging from 12 

 to 23 mm. high and 20 to 38 mm. wide. 



Horizon and locality .—-H-Mmlion. (Sellersburg) limestone: Charles- 

 town, Indiana and vicinity. 



DOLATOCRINUS BELLARUGOSUS Miller and Gurley. 



Plate 13, figs. 6-10. 



Dolatocrinus hellarugosus Miller and Gurley, Bull. 8, 111. St. Mus., 1896, p. 43, 



pi. 3, figs. 7-9. 

 Dolatocrinus coelatus Miller and Gurley, Bull. 8, 111. St. Mus., 1896, p. 46, pi. 



3, figs. 13-15.— Rowley in Greene, 1903, p. 165, pi. 48, figs. 10-12. 

 Dolatocrinus arrosus'MiLLEn and Gurley, Bull. 8, 111. St. Mus., 1896, p. 52, pi. 



3, figs. 22-24.— Rowley in Greene, 1903, p. 132, pi. 38, figs. 9, 10. 

 Dolatocrinus arrosus. var. cognatus Rowley in Greene, 1903, p. 137, pi. 39, figs. 



12-14. 



Base rather wider than in the last species. Ornament by radia- 

 ting striae with strong median ridges, more or less interrupted, and 

 rather prominent central nodes. Tegmen sharply lobed and more or 

 less spinous. The first three of Miller and Gurley's types are essen- 

 tially duplicates, with a difference of one arm; the others differ 

 slightly in proportions. I have 10 specimens besides, varying in 



