l88 SMITHSONIAN INSTITUTION 



from any of the others by the delicacy of the arms, and by the other details given. Figures 

 la, b show a specimen in which the surface markings are somewhat obscured ; that of figure 2 

 has the ridges very sharp and is strikingly similar to some specimens of P. patei, but the form 

 of the infrabasal ring will separate them. 



Type. Author's collection. 



Horizon and locality. Devonian, Keyser formation of the Helderbergian ; Keyser, West 

 Virginia. 



Pycnosaccus welleri n. sp. 



Plate XIII, figs. 3-5 



A small and delicate species, with low hemispheric calyx and relatively 

 long and heavy arms. Calyx without ridges or depressions of any kind; height 

 to width about 1 to 2 ; side outline convex, and surface evenly curved. Average 

 crown, 16 mm. high by 10 mm. wide at top of RR; base at column facet, 3 mm. 



IBB low, nearly horizontal, but little visible in side view, and not projecting 

 toward the column. BB small ; RR very large, three-fourths the height of the 

 calyx. R facets about one-half width of R, deeply excavated, with sharply 

 sloping shoulders at either side. IBr 3 to 4, sometimes 2. IIBr 4 to 6. Arms 

 rounded, long, and relatively heavy, tapering but little. Column moderately 

 large, composed of straight columnals of uniform width, with alternation of 

 shorter and longer ones for a short distance from the calyx, beyond which they 

 become of equal length. 



This species occurs in the same horizon and locality as P. patei. While not so abundant, 

 it is represented by a sufficient number of specimens to show the constancy of its characters. 

 It may be distinguished without difficulty, since it bears little resemblance to typical Pycnosac- 

 cus, the arms having increased at the expense of the calyx. Wherever in the stem or other 

 characters it departs from the type of Pycnosaccus it approaches Nipterocrinus, and without 

 the radianal and anal plate it would readily be taken for that genus. The increased number 

 of primibrachs is a well-established character, there being three or more in all the rays of 

 four specimens except in one ray which has two. 



Named in honor of Dr. Stuart Weller, of Chicago, whose work upon the crinoids of the 

 Chicago area is a notable contribution to our science, and who was the first to recognize the 

 presence of the genus Pycnosaccus in America. 



Types. Author's collection. 



Horizon and locality. Silurian, Niagaran Group, Brownsport limestone ; Decaturville, 

 Tennessee. A species of this type has recently been found in the Laurel limestone at St. Paul, 

 Indiana. 



Pycnosaccus americanus Weller 



Plate XIII, fig. 10 



Pycnosaccus americanus Weller, Bull. IV, Chicago Acad. Sci., pt. 1, 1900, p. 149, pi. 15, fig. 12 [Pycno- 

 saccus ornatus in explanation of plate 15L 



_ A small species of the type of P. scrobiculatus, but with a more elongate 



calyx, and especially much larger IBB, which are higher than in any other 



species. The specimen is too imperfect for detailed description. 



Type. Chicago Academy of Sciences. 



Horizon and locality. Silurian, Racine dolomite of the Niagaran Group; Chicago, 

 Illinois. 



