THE FOSSIL CPJNOID GENUS DOLATOCRINUS AND ITS ALLIES. 47 

 Form 4. AMPLUS group. 



Large, with broadly concave base; calyx plates tumid and rugose. 

 Arms 15 to 20. 



DOLATOCRINUS AMPLUS Miller and Gurley. 



Plate 11, figs. 11-17; plate 12, figs. 14, 15. 



Dolatoa-inus amplm Miller and Gurley, Bull. 5, 111. St. Mus., 1894, p. 45, pi. 



4, figs. C-S.— Rowley in Greene, 1903, p. 154, pi. 45, figs. 10-12. 

 Dolatocrinus vasculum Miller and Gurley, Bull. 6, 1895, p. 53, pi. 5, figs. 7-9. 

 Dolatocrinus peculiaris Miller and Gurley, Bull. 9, 1896, p. 55, pi. 3, figs. 28-30. 

 Dolatocrinus lyoni Wachsmuth and Springer, N. A. Crin. Cam., 1897, p. 314, 



pi. 25, figs. Qa-d. 

 Dolatocrinus pernodosus Rowley in Greene, 1903, p. 113, pi. 35, figs. 4-6. 

 Dolatocrinus tvachsmuthi Wood, Smithson. Misc. Coll., vol. 47, 1904, p. 77. 



A sharply defined form, well described by the authors under D. 

 amplus, with which they should have been content, without encum- 

 bering the literature with useless s^monyms, based wholly on varia- 

 tion in the number of arms from 17 to 20. Wachsmuth and 

 Springer described a typical specimen with 15 arms, which, accord- 

 ing to Miller and Gurley's major criterion, should be a good species. 

 Rowley added another with 17, because differently grouped; and 

 from my material now in hand I could swell the list with a new species 

 of 16 arms. Miss Wood contributed an additiomil name to replace 

 the preoccupied species of Wachsmuth and Springer. 



All these names and numbers stand for a single species, of a type 

 so distinctive in plan of sculpturing that it may be recognized from 

 a fragment containing a few plates of the dorsal cup. Instead of 

 being marked by radial ridges, striae, or more or less prominent 

 central nodes, all the plates are tumid or subspinous, radiately 

 vmnkled or furrowed toward the margins, to which they slope from a 

 a rounded or pointed center. The calyx is broadly truncate at about 

 the level of the second primibrach, from which it curves inward co 

 a broad concavity, involving the radials and part of the first inter- 

 brachials to about half the depth of the dorsal cup. It is subcylin- 

 drical from the level of the base up, and sometimes slightly constricted 

 below the arms. Tegmen rather low, subcorneal, smooth, or finely 

 pustulose; somewhat depressed or lobed in the interambulacral 

 spaces. The pinnule openings are conspicuous in the form of long 

 slits, two to each arm, and frequently four in the interrays. The 

 two outside ones are located well under the edge of the arm base, 

 and are often broken away. 



The species is of large size, ranging from 20 to 35 mm. high and 

 30 to 50 mm. ^\'ide, the relative height to width averaging about 

 1:1.3. 



In the broadly concave base, smooth tegmen, and prominent 

 ])innulo openings, tins form is nearest to T). ftteUifer. Besides the 



