DOLIOHORHYNOHUS INDICUS, A NEW ACRANIATE. 271 



The following tabulation of the genera and sub-genera of 

 Amphioxus will serve to show the systematic position of 

 the new form. 



Genus I. — Branchiostoma, Costa, 1834. 



With biserial gonads. 

 Sub-genus 1. — Amphioxus, Yarrell, 183G. 



Type, A. lanceolatus (Pallas). 

 Sub-genus 2. — Dolichorhynchus, n. g. 



Type, D. indicus, n. sp. 



Genus II.— Heteropleuron, Kirkaldy, 1895. 

 With uniserial gonads. 

 Sub-genus 1. — Paramphioxus, Haeekel, 1893 [in 

 Semon's ' Forschungsreise,' Bd. i, p. xiii]. 

 Type, P. bassanus (Giinther). 

 Sub-genus 2.— Epigonichthys, W. Peters, 187G. 



Type, E. cultellus, Peters. 

 Sub-genus 3.— Asy mmetron, E. A. Andrews, 1893. 

 Type, A. lucayanuni, Andrews. 



Of the above sub-genera the three which are most peculiar 

 in external form, namely, Dolichorhynchus, Epigonich- 

 thys, and Asy mmetron, are monotypic if we consider 

 Asymmetron caudatum, Willey, 1896, to be merely of 

 subspecific rank, as would seem to be the case. 



