230 EDWARD W. BERRY 



within the outer margins of the ambulacrals. The inter-abulacrals 

 are larger and there are ten normal pairs between the apex and the 

 ambitus. Length of the type 5.1 cm.; width 4.25 cm.; height 

 3.95 cm. 



These interesting and characteristic echinoids were figured as 

 early as 1565 and are a striking element in the later Upper Cre- 

 taceous faunas of Europe. They appear somewhat abruptly in 

 the Turonian, undergo but slight diversification in the Santonian, 

 and become exceedingly abundant and diversified in the Campanian. 

 They have dwindled to two known forms in the Maestrichtian and 

 have a single Danian and a single Eocene survivor. They evidently 

 found their optimum environment in the relatively clear and 

 shallow waters in which the chalk was deposited, which may account 

 for their singular rarity in the North American Upper Cretaceous 

 where such a large proportion of the sediments are muddy, thus 

 offering obstacles to both migration and colonization. In keeping 

 with this theory there is a single small species known from the 

 Vincentown Hme sands of the Rancocas formation of New Jersey, 

 Ananchytes ovalis Clark', and a second large species, Ananychites 

 texana Cragin^ from the Austin and Annona chalk in Texas and 

 Arkansas. Both are exceedingly rare and, so far as I know, are 

 represented by only the t3^e specimens. The Rancocas formation 

 was considered to be of Danian age by Clark'' although it is probably 

 Maestrichtian, and the Austin chalk should probably be correlated 

 with the Santonian or Campanian substages of Europe. A single 

 additional record of the genus in North America is an incidental 

 and queried reference by Aquilera'' to the presence of Ananchytes 

 sulcatus Goldfuss in the Upper Cretaceous of Mexico. 



Lambert's excellent monograph^ of the genus renders compari- 

 sons easy and this new Bolivian species is seen to somewhat resemble 



' W. B. Clark, U.S. Geol. Survey Bull. 97 (1893), p. 74, PL XXXVI, Fig. i a-h. 



^ F. W. Cragin, Fourth Ann. Kept. Geol. Surv. Texas (1893), P- i45> PL XXV, 

 Fig. 12; PL XXVI, Figs. 1,2. 



3W. B. Clark, Geol. Soc. Am. Bull., Vol. VIII (1897), pp. 315-58- 



1 J. G. Aquilera and E. Ordonez, Datos para la geologio de Mexico (1893), p. 27. 



5 J. Lambert, "Etude monographique sur le Genre Echinocorys," Mem. M its. 

 Roy. d. Hist. Nat. Beige, Tome 2 (1903). 



J 



