42 BULLETIN 115, UNITED STATES NATIONAL MUSEUM. 



should all be dumped into synonym} . The earlier species is ex- 

 ceedingly well marked by its general curvature, small basal pit, low 

 and strongly lobed tegmen covered with small tubercles, projecting 

 lip above the interrays, and uniformly 10 arms. All these features 

 the Hamilton forms have, so that one is struck by the resemblance 

 at the first glance, despite the difference in size, and can not help 

 feeling that this is a good example of the breaking up of specific lines 

 incident to the approaching extinction of the group. The speci- 

 mens are mostly of considerably larger size than those of the Onon- 

 daga species, and along with this the great variability in surface 

 markings may be taken as a character upon which to call Miller and 

 Gurley's variety a species. There are six good specimens besides the 

 type, and they include ornament by fine striate lines, wrinkles, tuber- 

 cles, or pits, with median radial ridge low and rounded, or concen- 

 trating in strong separate nodes on the radials and primary brachials, 

 or extending keel-like and sharp to the arms. The last form covers 

 Wachsmuth and Springer's D. marshi, var. homiltonensis , which in 

 the leading characters resembles this species more than the one with 

 which it was associated. n addition to Miller and Gurley's type, 1 

 have figured four specimens of this form as an object lesson upon 

 surface ornament in this genus. 



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

 town, Indiana, and vicinity. 



Form 2. BTTLBACETTS group. 



Ten-aiined; small, subglobose to oblate spheroidal. 



DOLATOCRINUS BULBACEUS Miller and Gurley. 



Plate 11, figs. 1-3. 



Dolatoainus hulbaceus Miller and Gurley, Bull. 4, 111. St. Mus., 1894, p. 2'J, pi. 



2, figs. 13-15. 

 Dolatoci'inus pulchellus Miller and Gurley, Bull. 0, p. 55, pi. 5, figs. 13-15. — 



Rowley in Greene, 1903, p. 109, pi. 33, figs. 16-18. 

 Dolatocrinus aspratilis Miller and Gurley, Bull. 9, 1S9(), p. 49, pi. 3, figs. 16-18. 

 Dolatocrinus subaculeatus Whiteaves, Contr. ("anad. Pal., vol. 1, 1898, p. 369, 



pi. G, figs. C, 6a. 



A small, subglobose form with .subpentagonal outline, well de- 

 scribed and figured by Miller and Gurley under the several specific 

 names above cited. Typically it is marked by sharp central nodes 

 on first interbrachials and radials, with a strong ridge connecting the 

 latter and forming the prominent rim of a broad pentagonal basal pit; 

 the sculpturing may vary from sharp to obscure, and the general form 

 from subglobose to oblate spheroidal. Arms 10. A well-defined 

 type and abundant. 



I 



