26 THE VOYAGE OF H.M.S. CHALLENGER. 



Heteropegma as an independent genus, since it seems to play in the Family of Syconidae 

 the same part as Leucetta (s.m.) amongst the Leuconidse, and this latter genus now 

 contains four very good species. The agreement in the plan of organisation of both 

 these genera is striking, and at first sight it would appear veiy likely that the genera 

 Leucetta and Heteropegma form an independent branch in the genealogical tree of the 

 Heteroccela, and consequently ought to be regarded as representatives of a new family. 

 Still, in order to render this hypothesis plausible, it would be necessary — in view of the 

 peculiarities of the internal organisation of Heteropegma nodus gordii (PI. IV. fig. la) — 

 to prove that the canal system of Leucetta has been developed from that of Heteropegma 

 not by invagination of the inner surface between the radial tubes, but by the further rami- 

 fication of the radial tubes themselves. Of course the possibility of such a transformation 

 is not excluded ; at any rate both are at present to be distributed in different families, 

 the more so as there exists a form (Leucetta imperfecta, n. sp.) which on vabd grounds can 

 be regarded as a connecting link between the genera Leucetta and Leuconia. 

 The genus includes provisionally but one species : — 



Heteropegma nodus gordii, n. sp. 



5. Amphoriscus, Haeckel 1 (sensu mutato) 



Syconidae with non-articulated tubar skeleton, the supporting spicules of whose com 

 paratively thin cortex are cither triradiate or quadriradiate, or both triradiate and 

 quadriradiate associated together. 



I include in this genus the following species: — 



Amphoriscus stauridia, H. 

 urna, H. 

 cyathiscus, H. 

 cylindrus, H. 

 chrysalis, S. 

 glacial is, H. 

 testiparus, H. 



Amphoriscus oviparus, H. 

 synapta, H. 

 sycilloides, Sch. 

 (?) atlanticus, R. 

 jwcidum, n. sp. 

 elongatus, n. sp. 

 flamma, n. sp. 



"VY ith regard to the systematic position of Syeyssa huxleyi, characterised by Haeckel 

 amongst others also as having a non -articulated tubar skeleton, one can frame only con- 

 jectures. As described by Prof. Haeckel, 1 this very strange form stands quite isolated. 



1 Prodromus, p. 238. 



