41 



from those that are generic; and, it is not improbable, that 

 another species may be found having a proboscis, and, if so, 

 the presence or absence of a jiroboscis will dwindle to specific 

 importance only. We refer the genus to the Actiiiocrinidw. 



SHOMAHDOCKiNus CONCINNUS, Shumard. 



Plate IT. Fiij. 7, hasdl view; Fig. 8, summit view; some of the 



plates are destroyed; Fig. 9, side view; Fig. 



10, azijgons side view. 



This species was described in 1855 by Shumard in these 

 words: 



"The portion of the body of this species situated above the 

 second radial pieces is unknown. 



"The inferior jjart of the calyx is nearly hemispherical, and 

 the plates moderately thick. Basal pieces, three, nearly equal 

 in size, forming a low cup with a nine-sided border, and pre- 

 senting beneath a wide, circular, shallow depression for the 

 column. First radials, moderately convex, length and breadth 

 nearly equal, three hexagonal and two heptagonal; inferior 

 angle of heptagonal pieces corresponding with a basal suture. 

 Second radials, wider than long, with the articular facets for 

 third radials nearly perpendicular, large, reniform, occupying 

 nearly half the length and two- thirds the width of each piece. 

 First interradials, hexagonal, a little longer than wide, and 

 rather larger than the second radials. First areal pieces, 

 hexagonal, longer than wide, its inferior angle corresi^onding 

 to a basal suture. Second areals, heptagonal, surface of the 

 plates ornamented with i)rominent radiating ridges, which rise 

 from near the center of the plates, and cross the sutures, so 

 as to form several sets of double triangles around the body." 



It will be observed, that Shumard thought he had only a 

 fragment of the calyx, whereas he had, in fact, a complete 

 calyx. He thought he had an Actinocrinus, as far as the sec- 

 ond radials, and that the third radials had been broken away, 

 but he had a new genus that never had any third radials. 



Meek and Worthen described Actinocrinus validus, in 1860, 

 in proceedings Acad. Nat. Sci. Phil. p. 3.S4; but in 1866, in 

 vol. 2 of the Geo. Sur. 111., p. 'l()i\ referred it to Actinocrinus 

 concinnus. Their species has but little resemblance, in any 

 respect, to Shumard' s, and it is not easy to understand why 

 —6 



