﻿ASYMMETRON.-RAFF. 



30s 



l^nuineratiiiii the species jjreviously found in the Austral- 

 asian seas, it will be seen that hitherto only one has been found 

 along the south coast of Australia, viz., .4. bassanuni. The 

 following is a list of the Australasian species niid iheir distribu- 

 tion, as set out by Mr. W. M. Tattersall, B.Sc.,i with the 

 addition of Professor Haswell's new species: — 



Branchiostoma helcheri, Gray. — 



Borneo, Singapore, Torres Strait, Maldixe Islands and 

 Ceylon. 

 Asynuuetron hasscuiHDt, Glinther. — 



Bass Strait, and as far north as Port Jackson. 

 .4. hcctori, Benham. — 



East coast of North Island of Xew Zealand. 

 A. ciiUt'Iliim, Peters. — 



Torres Strait, north-east coast of Australia, Thursday 

 Island and Ceylon. 



.4. lucayaniDu, Andrews. — 



Bahamas, Louisiade Archipelago, Maldive Islands, 

 Zanzibar and Torres Strait (Haswell). 



Hetcn>pJeui'0}i IialJeyi, Haswell. — 

 Torres Strait. 



As the species described differs entirely from A. bassanuni , 

 the only other species from the southern coast, it may be worth 

 while to here note the difference in general external appearance 

 between the two (PI. xxxvii., fig. 2). Roughly speaking, we 

 can say that in A. hassa)uini the widest portion of the body is 

 at about its middle third, and from here it tapers gradually 

 towards both ends. In A. australis, however, it appears 

 widest at about the second quarter from its anterior end, and 

 tapers gradually from here towards the posterior end and only 

 very little towards the anterior end. Thus the anterior half of 

 the animal is much wider than the posterior, whereas in .4. 

 bassanum the anterior and posterior halves are fairly equal. 

 This seems to be a most striking difference between the two 

 species. In addition, the smaller size of this species, and also 

 the absence of the incomplete ring of pigment alwa}s found in 

 A. bassanuni, mav be noted as further differences seen easily 

 with the naked eye. 



In comparing the oral hoods of the two species, an im- 

 portant difference is seen between them. As was noted above, 

 the most median ventral oral cirrus in .4. ausiralis is unpaired. 

 In .4. bassanum the arrangement of the mid-ventra.l portion 



1 Tattersall -Trans. Liverpool Biol. Soc, xvii., p. 293. 



