280 W. BLAXLAND BKNHAM. 



I regret that I have been unable to make a fuller exami- 

 nation of this interesting species, and look forward to obtain- 

 ing living specimens ; but it appeared worth while to rescue 

 these individuals from their obscurity when it was found 

 that they differed from those of the neighbouring seas. 



DUNEDIN; 



August 25 tl), 1900. 



EXPLANATION OF PLATE 17, 



Illustrating Professor Blaxland Benham's paper on 

 " Heteropleuron hectori, the New Zealand Lancelet." 



Fig. 1. — Heteropleuron liectori, n. sp. (x 2). a. Metapleur. h. 

 Floor of atrium, c. At.riopore. d. Anus. 



Fig. 2. — Heteropleuron hector i. Side view of the anterior end (x 

 8). a. Left metapleur. h. Floor of the atrium, c. Right metapleur. Tiie 

 outline of the rostral fin is dotted, as there is some doubt as to its true shape 

 and size. 



Fig. 3. — Hinder end of the same (X 8). a. Left metapleur. h. Atriopore. 

 c. Ventral fin. d. Anus. 



fxu. 4. — Ventral view of the anterior end of the same, showlni; the vesti- 

 bule opening distinctly on the left side of the animal, a. Left metapleur. h. 

 Floor of atrium, c. Right metapleur. d. Ventral fin. 



Pjg. 5.— a portion of the ventral base of the caudal fin of a transparent 

 specimen, seen under a low power, a. Muscles, b. Fin. c. Rod-like 

 structures, the walls of empty fin- ray boxes. 



Fig. 6.— View of the tail of H. bassanum, cleared in clove oil, showing 

 the post-anal continuation of the ventral fin rays. The myotome marked 3 

 is the antepenultimate segment, beyond wiiich the fin rays are absent, a. 

 Ventral caudal expansion of median fin, the edge of which is folded, b. Fin 

 rays. c. Dorsal portion of the caudal fin, along the base of which empty 

 "boxes" and lymph-spaces are seen. 



]?IG. 7. — A view of a portion of the per-anal part of the ventral fin of H. 

 bassanum. The lower part of the body was cut off, cleared and mounted ; 

 it is seen from below, and shows a single series of fin rays. 



