REPORT ON THE CRINOIDEA. 239 



We have seen that, alike in the ten-armed and in the bidistichate series, two very 

 distinct morphological types are to be found, the one with the rays flattened laterally 

 and a complete ambulacral skeleton, and the other without these characters. The first 

 of these, represented by the Basicurva- and Spinifera-gromps, is restricted almost 

 entirely to the continental and abyssal regions, and is especially characteristic of the 

 Pacific Ocean and Eastern Archipelago. One abnormal form occurs in the littoral 

 fauna of the Southern Australian Seas ; a few typical but isolated species have been 

 found at considerable depths in the Atlantic and Southern Sea ; while three more range 

 from 80 to 270 fathoms in the Caribbean Sea. Among the tridistichate species of 

 Antedon there are seven which have wall-sided rays and an ambulacral skeleton. Two 

 of them occur in the Philippine Archipelago ; a third was obtained at two (or perhaps 

 three) stations in the South Pacific ; the Challenger dredged two more at a station near 

 Ascension (Station 344), one of which was also found off Tristan da Cunha (Station 135g) ; 

 and yet two more appear in several of the " Blake " dredgings in the Caribbean Sea at 

 depths of 80 to 270 fathoms. These seven forms may be spoken of collectively as the 

 Granulifera -group, after the name of a Caribbean species which was described by 

 Pourtales in 1878 ; and they have essentially the same distribution, both bathymetrical 

 and geographical, as the Basicurva- and ^:»« (/era-groups, which are also distinguished 

 by wall-sided rays and an ambulacral skeleton. 



On the other hand, the tridistichate species of Antedon, which have unprotected 

 ambulacra and no flattening of the lower ray-joints (Savignyi-group), belong for the 

 most part to the littoral fauna of Northern Australia and the great Eastern Archipelago, 

 ranging northwards to Hong Kong and Japan. Individual species occur here and there 

 on the western shores of the Indian Ocean ; but I am not aware that there is any 

 tridistichate Antedon in the Atlantic or in the Caribbean Sea which has simple rays and 

 unprotected ambulacra. 



8. The Gra?iulifera-grou]). 



Tridistichate species with plated ambulacra and the lower parts of the rays flattened 

 laterally. 



Remarks. — Four of the five members of the Granidifera-grou-p which are 

 considered in this Report are constructed upon the same type as Antedon granulifera 

 itself. 



Neither the lateral flattening of the rays, nor the plated disk and ambulacral 

 skeleton of this species, seem to have attracted the attention of Count Pourtales when he 

 examined it, though they have since turned out to be characters of primary systematic 

 value. He described the type ' as having " three brachials between primary and 



1 Bull. Mus. Comp. Zool., 1878, vol. v. No. 9, p. 215. 



