The Generic Status of the New Zealand Lancelet.

In 1872, Hutton first recorded a lancelet in our waters as Branchiostoma lanceolatum Yarrell from material which Benham re-examined and recognised as a new species which he placed in the genus Heteropleuron Kirkaldy, 1895, as H. hectori. It has been known under this name to the present time in our literature. Unfortunately Heteropleuron was short-lived being reduced to a sub-genus of Asymmetron, and subsequently recognised as a synonym of Paramphioxus Haeckel 1893 which is now in turn recognised as a synonym of Epigonichthys Peters 1876. G. P. Whitley in his “Fishes of Australia. Part I” has proposed reference of H. hectori to a new genus—Zeamphioxus—which apparently includes only the New Zealand species. He has cursorily defined the genus as distinct in the high myotome count (53 + 19 + 12 = 84), etc., of hectori Whitley has established other genera for Australasian lancelets—three new genera for seven species. From his acounts, it is clear he regards combinations of the level of origin of the dorsal, the number of myotomes, a notch between rostral and dorsal, etc., as generic in value. Bigelow and Schroeder in their “Fishes of the Western North Atlantic” give a key to the thirteen species of the g. Branchiostoma. Following Whitley's practice, this genus would explode into some six genera which is not the view of the many workers in this group. Branchiostoma includes species having a myotome count as low as 62 (B. lanceolatum), up to 79 and more (B. elongatum); a notch, or none between rostral and dorsal, etc. In brief, Whitley's generic criteria are those elsewhere recognized as only of specific significance. A comparison of Benham's account, examination of a single specimen in our collection, shows satisfactory agreement with the g. Epigonichthys Peters 1876 to which our species should be assigned. Zeamphioxus cannot be viewed as holding generic status if hectori is the type. Accordingly the New Zealand species is transferred to the genus Epigonichthys and should be known as E. hectori (Benham).