278 W. RLAXLAND BEN HAM. 



It is scarcely necessary to state that the right metapleur 

 is continuous with the ventral fin, as that is one of the 

 characters of the genus. 



Locality. — East coast of the North Island of New 

 Zealand.^ 



From this brief but sufficient survey of the external 

 characters of the New Zealand species, it will be seen that it 

 differs from each of the previously known species of Hetero- 

 pleuron. 



In form this new species seems, from the drawings avail- 

 able, to be somewhat stouter than other species, while the 

 tapering anteriorly is comparatively sudden (fig. 1). The 

 greatest height, measured from the upper edge of the dorsal 

 fin to the lower margin of the metapleure, is 5 mm., which is 

 about one tenth of the total length. These measurements 

 are, of course, liable to variation according to the condition 

 of preservation ; ray specimens, however, are not shrunk in 

 the way that occurs when living specimens are plunged into 

 strong alcohol, but have retained a form similar to that of 

 A. lanceolatus preserved in picric acid, and though some- 

 what soft are not in any way " rotten.'" Therefore I think 

 the form given in the plate, which is drawn to scale, is as 

 nearly as possible true to life. It must be borne in mind, 

 however, that the pre-oral hood is retracted, while in the 

 most reliable drawing of Ampliioxus, viz. that given by Pro- 

 fessor Lankester, this hood hangs down as a nearly semi- 

 circular membrane. The left metapleural ridge can be 

 traced in my specimens right forwards above the hood, 

 which has shrunk upwards below it (see fig. 2). 



The distance between the atriopore and the anus is one 

 sixth of the total length, and the distance of the anus from 

 the end of the body is one sixteenth of the total. 



In size it exceeds the largest, which is H. bassanum, 



' According to a verbal communication by Sir James Hector, these two 

 specimens were collected at Awanui, just south of tlie East Cape ; whilst 

 Huttou in the 'Catalogue' gives as the locality "Poverty Bay," which is a 

 little further south. 



