126 



DISCOVERY REPORTS 



The Discovery collection contains many specimens of Isometra vivipara and Noto- 

 crinus virilis ; there is one male of Phrixometra nutrix from the Bransfield Strait in the 

 Antarctic. 



The following table includes these three species and the seven species and one 

 variety which are shown in this paper to be viviparous ; it is a complete list of the known 

 viviparous crinoids.' The localities from which each is recorded are shown. 



The table includes two species, Eumorphometra concinna and Phrixometra longipinna, 

 which were not taken by the Discovery vessels. I owe my knowledge that the former is 

 viviparous and the opportunity of describing its brood-pouches to Mr A. H. Clark: 

 when he heard from me how many viviparous forms I was finding he re-examined 

 Eumorphometra concinna, saw that the female had brood-pouches and immediately sent 

 me some. Carpenter had described " much swollen ovarian " sacs in Phrixometra longi- 

 pinna ; I found them to be brood-pouches. 



The table shows that of the eleven viviparous forms eight are known only from the 

 Antarctic. One is known from the Antarctic and the Burdwood Bank, another from 

 the Antarctic, the Burdwood Bank and the east coast of South America as far north as 

 the River Plate. One is known from off the River Plate only. 



If the table be compared with the list on p. 1 23 it will be seen that of the nineteen 

 comatulids known from the Antarctic ten, over 50 per cent, are viviparous. More than 

 600 species of unstalked crinoids are known from other seas and only five of them, two 

 of which also occur in the Antarctic {Isometra vivipara and Phrixometra nittrix), are 

 viviparous ; the other two are P. longipinna and the two viviparous forms from southern 

 Australia. 



The percentage of viviparous forms from the Antarctic may be considerably higher. 

 All the Antarctic species of the Notocrinidae and the Isometrinae, but only four of the 

 eight species of the Zenometrinae and Bathymetrinae, are viviparous. But the re- 



^ Since this was written two species from southern Australia have been described as viviparous 

 (H. L. Clark, 1938, Echinoderms from Australia, Mem. Mus. Comp. Z06I., LV, pp. 40-1). 



