CLARK.] CIDARLS TAYLOKENiSIS. 35 



of the yellow limestone of the middle iharl bed (upper Cretaceou.s). 

 It has also been fonnd by the writer near Vineentown in the same 

 formation. 



CoUcrtions. — Philadelphia Academy of Natural Sciences; Johns Hop- 

 kins University. 



CiDARIS TAYLORENSIS Clark, 

 Plate VI, Figs. 2((r-b. 



Bi'termi native characters. — Test small. Interambnlacral areas wide. 

 Tubercles large, with circular areolas, much depressed marginally; 

 boss crenulated ; mamelon perforated. Mihary space narrow. Spines 

 long, cylindrical, covered with small granules arranged in longitudinal 

 rows. 



Dimensions. — Test undetermined. Spines : length 1^ inches ( 1) ; width 

 in broadest portion, i^,.; inch. 



Description. — The fragments of this form, although they admit of 

 determination of but few of the important characters, warrant specific 

 description from the fact that they are totally distinct from the only 

 other rei)resentative of Cidaris from the Jurassic rocks of America. 

 The small fragments of the interambulacral area and the spine occur 

 together and doubtless formed i>art of the same individual. The inter- 

 ambulacral plates, of which only portions are preserved on the specimen 

 figured, indicate a form of no great size (PI. vi, Fig. 2a). The tubercles 

 are large, with depressed areolas surrounded by a circle of large gran- 

 ules. The boss is crenulated and tlie mamelon perforated. The miliary 

 space is ajjparently narrow, the tubercles of adjacent plates in the same 

 column being nearly confluent. 



The spine is long, gently tapering toward the base in the portion 

 preserved, and covered with longitudinal rows of small granules (PI. 

 VI, Fig. 2b). 



Related forms. — As the Jurassic strata of North America afford few 

 fossil Echinodermata as compared with the Clretaceous, there are not 

 many American types with which the present form may be compared. 

 C/V/am crt?t/or;>^'Q^, the only other represeutativ^e of this genus thus 

 far reported, ha^i no portion of the test ])reserved, so that the compjirison 

 is limited to the spines. In C. taylorensis the spines are long and 

 cylindrical, while in C. californicus they are short and thick set, and 

 there is a totally dift'erent surface decoration. 



Locality and geological horizon. — Tliis speciiis is known only from the 

 Jurassic strata of Taylorsville, California, \J 



Collection. — U. S. National Museum. 



