TKIASSIC ECHINODERMATA. 23 



Class STELLEKOIDEA. 



Subclass OPHIUROIDEA. 



Order ZYGOPHIUR^E. 



Family AMPHIURID^E. 



Genus ASPIDTJRA Agassiz. 



Aspidura ( ?) IDAHOENSIS Clark, n. Sp. 



Plate I, figure 4. 



Determinative characters. — Casts of small forms, with short arms. Very poorly preserved. 



Dimensions. — Diameter of disk 5 to 7 millimeters; length of arms 10 to 25 millimeters. 



Description. — Three individuals of this species, all in a very imperfect state of preservation, 

 have been examined. They occur as partial casts of the disk and rays. The characteristics of 

 none of the plates can be seen. The general outline of the disk and rays remains constant in all 

 the specimens, which evidently belong to the same species. 



Locality. — One and one-half miles west of Paris, in the first canyon north of Paris Canyon, 

 Bear County, Idaho. 



Geologic horizon. — Thaynes limestone, Lower Triassic. 



Collection.— U. S. National Museum (31187). 



Class ECHINOIDEA. 



Subclass REGULAEIA ENDOBKANCHIATA. 



Order CIDAROIDEA. 



Family CIDARID.E. 



Genus CIDARIS Leske. 



Cidaris shastensis Clark, n. Sp. 

 Plate I, figure 5. 



Determinative characters. — Test apparently large. Interambulacral areas wide. Tubercles 

 large, circular, with depressed areolas; miliary space large. 



Dimensions. — Width of fragment 10 millimeters; height of fragment 6 millimeters. 



Description. — The single fragmentary interambulacral plate found indicates that this species 

 possessed a test of considerable size. The interambulacral areas are wide, the tubercles large, 

 circular, and with depressed areolas. The miliary space is large. The plate is probably from 

 near the ambitus. The broken tubercle renders it impossible to say whether the mamelon was 

 perforated or not. There is no trace of the plates of the ambulacral area. 



Related forms. — Species is shown by the wide miliary space to be quite distinct from C. dil- 

 leri. It is evidently a new species. 



Locality. — Two and one-half miles west of Kound Mountain, Shasta County, Cal. 



Geologic horizon. — "Cedar formation," Upper Triassic. 



Collection.— \J . S. National Museum (31188). 



Cidaris dilleri Clark, n. sp. 



Plate I, figure 6. 



Determinative characters. — Test apparently of medium size; ambulacral areas narrow, flexu- 

 ous, with two rows of granules between the poriferous avenues; interambulacral areas of mod- 

 erate width. Tubercles of medium size with oval areolas; boss crenulated; mamelon perforated; 

 miliary space narrow. 



