76 MESOZOIC ECHINODERMATA OF THE UNITED STATES. [bull. 97. 



(lenly terminated by the nearly vertically truncated surface of the 

 X)Osterior margin. The sides decline equally to the ambitus, giving- an 

 oval outline to the vertical lateral section. The lower surface is nearly 

 flat, with the exception of the slight depressions directly at the mouth 

 edges and the elevated area extending from the center of the base to 

 the i)osterior margin. 



The ambnlacral areas are wide, apetaloid, and separated at the apex. 

 The anterolateral pair are bent backward in their upper part, beyond 

 which they extend straight to the margin. The postcro lateral pair 

 are bent somewhat forward, after which they extend straight over the 

 margin. The single ambulacrum is situated in the deep anterior sulcus. 

 The i)ores of the paired ambulacra consist, in the upper portion of the 

 columns, of oblique oval openings united by furrows (PI. xxxvii. Fig, 

 If), while lower down they become small and often indistinct (PI. 

 XXXVII, Fig. 1/). In the unpaired ambulacrum the pores are extremely 

 sm.all. 



The surface of the interambulacral as well as of the ambnlacral plates 

 is covered with fine granules, among which are irregularly scattered 

 numerous small perforated tubercles. 



The apical disk is narrow, elongated. The four perforated genital 

 I)lates are disjiosed in jiairs, between which two of the five ocular plates 

 are situated. Forming the posterior portion of the disk are two more 

 ocular plates, while the fifth plate comprises the anterior part. The 

 ambnlacral areas are on this account separated at their apices (PI. 

 XXXVII, Fig. 1/i). 



The mouth opening is transversely oblong and is situated near the 

 anterior margin of the base. The anal opening is oval and situated on 

 the truncated surface at the posterior margin of the test (PI. xxxvii. 

 Fig. le). 



Related forms. — This species is separated from ITolasfer simplex, the 

 only other closely related form found in American Mesozoic deposits, 

 by its deep anterior sulcus and less inflated upi)er surface. 



Locality and geological horizon. — (Jardiaster cincius is from the yellow 

 limestone of the middle marl bed (upijer Cretaceous) of Timber creek, 

 New Jersey. 



Collections. — Philadelphia Academy of Natural Sciences; American 

 Museum of Natural History, New York. 



HOLASTER Agassiz. 



HOLASTER SIMPLEX Shumard. 



Plates XXXVIII, Figs, la-g; xxxix, Figs. la^d. 



Holaster simplex Sbnm.ard, 1853. Kept. Expl. Red River of Louisiana in 1852, p. 210, 



PI. 3. Fig. 2. 

 Holaster comanchesi Marcon, 1858. GeoL of North America, p. 40, PI. 3, Fig. 3. 

 Holasier simjtJex Desor, 1858. Synop. rtes Echinides fossiles, p. 450. 

 Holaster comanchesi Dosor, 1858. Synop. des Echinides fossiles, p. 449. 



