THE FOSSIL CRINOID GENUS DOLATOCRINUS AND ITS ALLlliS. 39 



With 10 to 20 arms— Continued. 



Small to medium size — Continued. 



Calyx large, subcyUndrical; base broadly concave, without 

 pentagonal rim. All plates of cup tumid, rugose, radi- 

 ately furrowed or wrinkled, sloping from margin to cen- 

 ter. Tegmen subconical, .smooth. Pinnule openings 

 conspicuous. 

 Tegmen somewhat lobed . 



Arms 15 to 20 D. amplus. 



— vasculum . 

 — pecaliaris 

 — lyoni Wachsmuth and Springer. 

 — pernodosus. 

 — wachsmuthi. 

 Tegmen less lobed. Wrinkles on cup plates rather ir- 

 regular. Arms 20, in nearly continuous ring D. costatiis. 



Calyx of medium size, more or less rotimd above; base trun- 

 cate, with narrow pit. 



Radiating striae strong, those on iBr and radials form- 

 ing a conspicuous star aroimd the basal pit. 



Tegmen not lobed; low. convex, rugose. Pinnule 



openings conspicuous. Arms normally 15 D. asterins. 



Radiating striae sharp, forming triangles, but not 

 sharply defined star; ridges not prominent. 

 Tegmen rugose, broadly lobed. Pinnule openings 



obscure. Arms 20 D. incisus, new species. 



Calyx small to mediiim size; bowl-shaped, hemisperoidal, 

 not constricted below arms; sides ciu'ving evenly upward 

 from narrow base. Tegmen lo\v. Pinnule openings not 

 conspicuous. Arms 15 to 20. 



Medium size; strong nodes radiatel>- arranged, or inter- 

 rupted ridges on plates, without fine striae D. venustus. 



— aureatus. 

 — lyoni Miller and Gurley. 

 — corbuliferus. 

 Fine striae forming triangles. 



Tegmen strongly lobed, and more or less spinous D. hellunicjosus. 



— coelatus. 



— arrosus. 



— var. cognatus. 



— depressus. 



Small; radial ridges higli and sluiip. with fine striae. Arm? 



mostly about 20 D- cronuitus. 



— dispar 



Insufficiently known . Arms 15 D. canadensis. 



Calyx large to medium size. Bursiform, constricted below the 

 arms; base truncate, broad, flat, or shallow concave; tegmen 

 more or less lobed; pinnule openings often inconspicuous, 

 usuallv 2 to each arm base, may be 4 to the interray. 



