ORTMANN I TERTIARY INVERTEBRATES. 51 



SYSTEMATIC PART 



ECHINODERMATA. 



ECHINOIDEA. 



Fam. CIDARID^E Wright. 



Gen. CIDARIS Klein, 

 i. CIDARIS ANTARCTICA Ortmann. 



PI. XI, Fig. i-*. 



1900 Cidaris antarctica Ortmann, in: Amer. Journ. Sci., v. 10, p. 369. 



Only isolated interambulacral plates and spines. 



Plates with a moderately large, perforated central tubercle, the neck of 

 which is slightly and indistinctly crenulated. Scrobicule large, surrounded 

 by a circle of small tubercles, between which there are, irregularly scat- 

 tered, still smaller ones. Spines subcylindrical, mostly slightly compressed, 

 so as to render the cross section elliptic ; neck somewhat constricted. For 

 the rest, the different fragments are of about the same thickness through- 

 out their length. Articular surface conical, finely striated, with a deep 

 articular groove. Surface of spines closely covered with fine, rounded 

 granules, forming irregular longitudinal rows. The granules are evenly 

 developed all around the spine : but there are four spines from Lake 

 Pueyrredon, which show larger, irregular, conical, subspiniform tubercles ; 

 in two of them these tubercles are found only on one side of the spine. 



Record of specimens : Mouth of Santa Cruz River, 8 spines ; San Julian, 

 Oven Point, i spine, i plate ; San Julian, Darwin Station, 3 spines ; 30 

 miles north of Rio Chalia, 4 spines, 5 plates ; Lake Pueyrredon, base of 

 Tertiary, 17 spines, 3 plates. 



Affinities: Similar spines are known in Cid. avenionensis Desm. (Mio- 

 cene of France and Switzerland, see: Loriol, 1875, p. 15, pi. i, f. 8-13, 

 especially Figs. 10, 11, 13), but these differ in the necks not being con- 



