OPALINID CILIATE INFUSORIANS — METCALF 577 



These forms, grouped together to indicate the later steps in the 

 development of Protoopalina into Cepedea, are of eastern Asian and 

 Malaysian distribution, probably indicating the origin of Cepedea 

 there or in some nearby, connected region. 



There is one noteworthy feature of the distribution of Protoopalina. 

 Only a single species is reported from any of the lands reputed to have 

 been once united to form the Indian Ocean continent I-emuria (Mada- 

 gascar, the Seychelles, Ceylon, southernmost India). The one 

 instance is P. caudata microhyla, in Microhyla ornata, from Harnai, 

 Ratnagiri District, south of Bombay, "among mountains." This 

 location is about on the boundary line between the northern Indian 

 and the southern Indian faunas. Its host belongs to a southern 

 family, the Gastrophrynidae. This is the nearest approach to 9 

 record of a Protoopalina from Lemurian lands. Why are there no 

 more Protoopalinas in these Indian Ocean lands? Study of paleo- 

 geographic maps by Arldt and others (fig. 142, a) shows Indian 

 Ocean l^nds connected in Triassic times with Africa and Australia, 

 not with Malaysia. Lemuria is shown connected with Ethiopia, but 

 not with Asia-Malaysia during the Jurassic and early Cretaceous 

 periods. Madagascar separated from Ethiopia after the early 

 Cretaceous and probably did not join it again after this time (see 

 Hewitt, 1922, who suggests temporary late Tertiary connection). 

 The mid-Cretaceous island of India (fig. 143, b) is shown uniting with 

 continental Asia late in the Tertiary (fig. 145, a) and retaining this 

 connection until the present time. The only suggestion the author 

 can make is that Protoopalina was once in Lemuria but was extermi- 

 nated during the subsidences that broke it into several islands and 

 island groups, but that, before the middle Cretaceous period, somewhat 

 elongated Protoopalinas gave rise to Cepedea in Asia-Malaysia, which 

 was in contact with Lemuria for a period long enough to allow 

 Lemuria to become inhabited by Cepedea (fig. 143, a). 



THE GENUS ZELLERIELLA (Fig. 136) 



Species distinctions in this genus are difficult, though the genus 

 itself is well demarcated from the other genera. Its origin from 

 Protoopalina is indicated by a Protoopalina stage in its early develop- 

 ment (cf. Z. brasiliensis from Crossodactylus gaudichaudii, fig. 38). 

 Its geographical distribution, South America, Central America, and 

 Australasia, indicates its origin in the Southern Hemisphere and in 

 that land-complex which in late Cretaceous or early Tertiary times 

 included Australasia, Antarctica, and southern South America, pos- 

 sibly also South Africa early in this period. Comparative numbers 

 in the Australasian and South American regions suggest the origin 

 of Zelleriella in the region of greater Antarctica connected with 

 Patagonia and its migration westward from Patagonia to Australia. 



166877—40 8 



