46 BULLETIN 115, UNITED STATES NATIONAL MUSEUM. 



"15-armed species/' is described with ''four ovarian slits between 

 each {sic) radial series^ and two between each (sic) of the ambulacral 

 openings, which gives to this species 40 ovarian apertures;" but 

 among the cotypes selected by the authors are three specimens with 

 only two openings either between the rays or their divisions, and 

 among 16 other specimens with 15 arms, 11 have two and four 

 openings, and four have only two to each interval. The same thing 

 applies to D. laguncula, the "14-armed species," which among five 

 specimens has two with two and four openings, and three Vv'ith only 

 two. So if the species were to be arranged according to this char- 

 acter it would throw together forms with 11, 13, 14, 15, and 16 arms 

 in one species, and forms with 13, 14, 15, 16, and 17 arms in another. 

 As to these openings, the number observed depends somewhat upon 

 the preservation of the specimen and the level at which the arms are 

 detached ; two of the openings in the interrays are well exposed in the 

 median part, and always very plain, but the other two often lie close 

 under the arm bases, and if the lu*st pair of arm brachials are broken 

 off these openings ma}^ not be seen. It is probable that there were 

 normally four openings to the interrays, tv\'o of which may not always 

 be observable for the reason stated. 



The species is of medium size, ranging from about 12 to 20 mm. 

 height of calyx to where the tube becomes defined, and 18 to 32 mm. 

 in greatest width, the average height to width being about as 1 :1.6. 



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

 ville, Kentucky, and vicinity. 



DOLATOCRINUS TKIADACTYLUS Barris. 



Plate 11, figs. 9, 10. 



Dolatocrinus triadactyhisB arris, Proc. Acad. Sci., Davenport, Iowa, vol. 4, 1884, 

 p. 100, pi. 2, figs. 5-7. — Wachsmuth and Springer, N. A. Crin. Cam., 1897, 

 p. 316, pi. 26, figs. ia-d. 



This form, from the Traverse beds of the Michigan Hamilton, 

 belongs to the stellifer group, having the same excavate base, high, 

 smooth tegmen, and the same type of sculpturing, including both 

 fine and coarse striae, with a pentagonal rim bounding the basal cav- 

 ity. It differs in having a strongly lobed tegmen. The 15 arms are 

 constant in 23 out of 29 specimens, four others having 14, and two 

 16, aU bemg from the same vicinity. It ranges in size from 7 to 23 

 mm. high, and 8 to 28 mm. wide. Especially among the smaller 

 specimens, the calyx is relatively higher than in the Louisville form, 

 so that the average height to width is here about 1 : 1.25. 



Horizon and locality. — Hamilton (Traverse) shales: Alpena, 

 Michigan . 



