222 ABYLA HAECKELI. 



Their apparently trigonal form is diagnostic, but, as Haeckel observed, this form 

 is apparent rather than real, because the right lateral ridge, though insignificant, 

 can be traced at least for the lower one third of its course. The importance of 

 the posterior nectophore in classification, has already been discussed (p. 214). 



The identity of the Amphiroa alata of Huxley, from Torres Straits with 

 the corresponding Eudoxid from the Atlantic described by Blainville, Gegenbaur, 

 and Haeckel has been maintained recently by Lens and Van Riemsdijk; and 

 comparison of the present series with a collection from the West Indies shows 

 that they were correct. Gegenbaur, who traced the development of Amphiroa 

 alata proved that it is the Eudoxid of A. trigona. The bracts, even before their 

 detachment, show the characteristic "Amphiroa" structure, (Haeckel, '88b). 



A. trigona is widely distributed over the Mediterranean and the warmer 

 portions of the Atlantic, as well as the Eastern Tropical Pacific, and the Malaysian 

 region. Apparently it has not been recorded from the Indian Ocean; but in 

 view of its known distribution it may be expected to occur there. 



Abyla haeckeli Lens and Van Riemsdijk. 

 Plate 13, fig. 1, 2. 



Abyla haeckeli Lens and Van Riemsdijk, :08, p. 32, pi. 5, fig. 39— iL 



Abyla trigona Huxley, '59, p. 47, pi. 3, fig. 1 (non Qdoy and Gaimard, '27). 



? Amphiroa angulala Huxley, '59, p. 64, pi. 5, fig. 2. Eudoxid. 



1 Abyla alata Haeckel, '88b, p. 156 (non Amphiroa alata, BLArN\aLLE, '30). 



? Amphiroa dispar Bedot, '96, p. 373, pi. 12, fig. 5, 6. Eudoxid. 



Station 4634 300 fathoms to surface 1 anterior nectophore. 



" 4646 " " " " " " " 



" 4665 " " " " " " " 



" 4fifiS " " " " " " " 



4729 " " " " 



" 4746 " " " " " " " 



These detached anterior nectophores, 5-6 mm. long, agree very well in 

 their ridges and facets, with the detailed account of A. haeckeli given by Lens 

 and Van Riemsdijk. The inclusion under this species of the specimen from 

 Torres Straits described by Huxley ('59, p. 47) as A. trigona, rests upon his very 

 clear account of the structure of the nectophore, from which it is evident that 

 in his example there were two ventral facets separated by a transverse ridge, 

 instead of the single ventral facet of the true ^4. trigona. 



The comparison between the anterior nectophores of the two species by 

 Lens and Van Rienasdijk is so detailed that to go over the ground again here 



