314 J. W. KIRKALDY. 



Other characters apparently as in A. c a rib sens and A. 

 lanceolatus. 



Maximum length among four specimens 5 cm. (J. W. K.). 



Distrihiition. — Coast of Borneo (Sir Edward Belcher); 

 Prince of Wales Island^ Torres Straits (Dr. Coppinger). 



Remarks. — The only known specimens of this species are 

 preserved in the British Museum, Natural History. 



Sub-genus 3. — Heteropleuron. 

 Heteropleueon, J. W. K., sub-genus nov. 



The left metapleur terminates immediately behind the atrio- 

 pore ; the right is directly continued without interruption 

 into the median ventral fin. 



Ventral fin chambers with or without fin-rays. 



Gonad pouches limited to a single series, which is developed 

 on the right epipleur. 



Intra-buccal cirrhi sixteen in number. 



1. Heteropleuron Bassanum, PI. 34, fig. 6. 



Branchiostoma Bassanum, Giinther. ' Beport Zool. Coll., H.M.S. 



"Alert/" 1884, p. 31. 



Myotomes, maximum number 78, minimum number 70, 

 usual number 75 (in 50 specimens, J. W. K.). 



Myotome formula 43, 16, 12 ; 44, 14, 17 ; 45, 17, 15 ; 45, 

 16, 14 (usual). 



Dorsal fin shallow. Rostral fin large, and marked oflP from 

 the dorsal fin by a dip. Caudal fin long and low, the superior 

 and inferior angles entirely removed (as compared with A. 

 lanceolatus). Ventral fin with fin-ray chambers and paired 

 fin-rays. Prseoral cirrhi from 31 to 33 (in specimens examined). 

 Olfactory pit present. Oral sphincter underlies apex of seventh 

 myotome. lutra-buccal cirrhi sixteen in number. Gonads 

 26 — 31, only present on the right epipleur. 



Maximum length of 50 specimens 4*3 cm. (J. W. K.). 



Distribution. — Bass's Straits, Australia. 



Remarks. — The specimens of H. Bassanum sent by Pro- 



