516 rROCEEDINGS OF THE XATIOXAL MUSEUM vor,. 89 



terior basal is considerably longer than that with the riglit posterior 

 basal. The radianal extends upward to approximately two-thirds the 

 height of the r post R. Anal X rests on tlie r post B on a narrow 

 face and contacts r post B on a considerably longer face. Anal X 

 extends npward above the plane of the radial facet. The right tube 

 plate is large, resting on RA on a relatively narrow face, and extends 

 npward above the plane of the radial facet by about two-thirds its 

 lieight. 



There is a single primibrach in each radius. The primaxials are 

 heavy, with long axillary faces. The lAx m the r and 1 post and 

 ant RR are considerably higher than those in the other rays. The 

 lAx ai-e constricted medially, and there are inconclusive indications 

 that each is composed of two fused primibrachs. 



The rami are relatively short and stout. Typically there is but a 

 single isotomous division above the main dichotom. In one specimen 

 in one half-ray there is an additional bifurcation resulting in an 

 endotomous structure. The divisions in the half-rays take place in 

 medium-sized specimens at about the eighth or tenth secundibrach, 

 but exceptionally it may come considerably higher. Owing to the 

 height of the brachials the division is high up, nearly at one-half 

 the height of the arms. The brachials are high, nearly quadrangular 

 in tlie distal portion of the ramus and with slightly sloping faces 

 proximad. Pinnules are borne on alternate sides by successive 

 brachials. The secundaxils are tumid to subspinous, giving the rami 

 a decided flexure at this level. The terminal rami are divergent at 

 their inception, which, combined with the outward flexure of the 

 IIAx, makes this portion of the arms quite prominent. These char- 

 acters become more pronounced with age. The pinnules are long 

 and stout. 



The ventral sac has been seen in but one individual, a young speci- 

 men here figured. The sac is short and slender, apparently having 

 a height of but about one-half that of the arms. It is reflexed, but 

 how far down on the anterior side the reflexed portion extends is not 

 known. 



The cohunn is circular in section, with well-defined nodals and 

 internodal series. 



Ty'pe. — The holotype, S 4401a, and paratypes, S 4401b-f, are in 

 the Springer collection in the United States National Museum. 



Horizon and locality. — The species has been found onl}^ in the 

 formation known as Ste, Genevieve in the Alabama geological re- 

 ports. All specimens were collected ai)pr<)ximately 7 miles south of 

 Huntsville, Ala. 



Relationshi'ps. — Dinotocrinus coinpacfus may readily be distin- 

 guished from D. roemei'i (Troost) from the same region. In sx)eci- 

 mens of comparable size the arms of D. roemeii are relatively stouter 



