122 Transactions. — Zoology. 



be regarded as a separate item in this species ; it is, indeed,, 

 merely the undifferentiated part of the median fin, and is very 

 short. Whereas in B. lanceolatum and in E. bassanum the 

 ventral fin is provided with paired fin-rays, in the present 

 species there are no ventral fin-rays, though fourteen fin-ray 

 boxes exist. Another peculiarity hitherto unnoticed in the 

 genus is the continuation of the fin-ray boxes, though without 

 fin-rays, along the base of the caudal fin, both dorsally and 

 ventrally, right to the end of the body. In the best-studied 

 form, from the Mediterranean, such structures are absent, or, 

 at any rate, have escaped observation, the fin-rays and their 

 boxes being confined to the dorsal and ventral fins. In the 

 present species, then, there is less differentiation of this 

 median fin than in other cases. 



A full and illustrated account of this interesting little 

 marine fish-like form will appear shortly elsewhere ; but I 

 append an outline drawing, in order that naturalists having 

 the opportunity may recognise this the lowest member of the 

 vertebrate race of animals. The species may be looked for at 

 low tide in sandy shores, or possibly in fine gravel.* 



EXPLANATION OF PLATE I. 



Heteropleuron hectori, n. sp. View of the left side; three times natural 



An., anus. s,ze - 



Atp., atriopore. 



c.f., caudal fin. 



fl., floor of atrium. 



My., Muscle-segments (myotomes), of which only a few at each end and 



in the middle of the body are indicated. 

 Mp., Left metapleural ridge. 



Art. VII. — An Account of Acanthodrilus uliginosus,. 



Hutton. 



By W. Blaxland Benham, D.Sc, M.A., F.Z.S., Professor 

 of Biology in the University of Otago. 



[Read before the Otago Institute, 13th November, 1900.1 



Plate V. 



In my " Be-examination of Hutton's Types of New Zealand 

 Earthworms " (1) I mentioned the fact that I had been unable 

 to find the "type" of " L. uliginosus ." I Since that date, 



* The specimens referred to were collected one at Awanui, near the. 

 East Cape, and the other on Mahia Peninsula, Hawke's Bay. — Ed. 

 f Trans. N.Z. Inst., vol. xxxi., Art. xix. 



