176 AETHUR WILLEY. 



Chlamydothorax. But, to avoid confusion, it is more con- 

 venient at present to regard these as sub-genera of the genus 

 Ptychodera. , 



Ptychodera (sensu strict o) has rudimentary genital pleura ; 

 to it belong P. minuta, Kowalevsky, and P. Sarniensis, 

 Koehler. 



Tauroglossus is distinguished by the dorsal origin of the 

 genital pleura; and to it belong T. apertus, Spengel, T. 

 claviger, Delle Chiaje, T. gigas,Fr. Miiller^T. aurantiacus, 

 Girard, and T. australiensis. Hill. 



Finally, Chlamydothorax is characterised by the ventral 

 origin of the genital pleura ; and to it are assigned Ch. 

 ery thrseus, Spengel, Ch. bahamensis, Spengel, and probably 

 Ch. ceylonica, Spengel, although the last-named species is 

 only referred to in Spengel's monograph, and not fully 

 diagnosed. 



From the account given above of P. flava, it is at once 

 evident that its place is under the sub-genus Chlamydo- 

 thorax. 



The fact of its close affinity to P. bahamensis instead of 

 to its neighbour, P. australiensis, of New South "Wales, is 

 interesting in connection with the fact that the Amphioxus 

 (Asymmetron caudatum) which I obtained from the Loui- 

 siade Archipelago, and described in a previous communication, 

 is likewise much more closely related to the Bahama species 

 (A. lucayanum, Andrews) than to the Australian forms. 



Conclusions. 



My investigation of P. flava, necessarily somewhat super- 

 ficial, has nevertheless sufficed to establish its systematic posi- 

 tion, but would hardly allow me to engage in an extended 

 morphological discussion. Still there are a few points upon 

 which one might venture an opinion, especially since it is 

 impossible to have once seen the free, erect, upstanding 

 pharynx of P. flava without being deeply impressed. 



Moreover the account, admirable enough, which Spengel 



