402 MONOGRAPH OF THE AUSTRALIAN MARSIPOBRANCHIl, 



the extremity of the snout ; the anterior portion of the fin is 

 small and evenly convex, and passes imperceptibly into the dorsal 

 integument at both ends, the length of its base is from 1 to 1^ 

 in the interspace between the two divisions of the fin and 24 to 

 2i in the base of the second portion, which is connected with the 

 caudal fin by a more or less conspicuous rayless membrane ; * the 

 lower lobe of the caudal is more developed than the upper, to 

 which it is joined round the extremity of the tail by a membrane 

 similar to that which connects it with the dorsal. Head and 

 body without conspicuous pores. 



In the ammoccete both the dorso-caudal and the intercaudal 

 membranes are well developed and the dorsal is continuous, but 

 in large examples the intervening membranes have entirely 

 disappeared. 



In the Nepean specimen (125 millimeters) the dorsals are con- 

 nected by a low cutaneous fold, as also are the second dorsal and 

 caudal, the fold in this case being almost as high as the latter fin 

 but rayless; the lower lobe of the caudal extends forwards to the 

 vent, and there is also a distinct fold for a considerable distance 

 in front of the vent ; the maxillary teeth are as large as in the 

 adults. 



Upper surfaces rich olive brown, the sides golden brown, lighter 

 below ; lower surface of the head and the throat silvery ; fins 

 greenish yellow. 



Castelnau's description of the colours, taken from a recent 

 specimen, is as follows : — 



" Bluish gray, darkest on the back; head yellowish; eye silvery; 

 first dorsal gray ; second bordered with pink, its jiosterior part 

 black ; caudal black, with a pink margin." 



The earliest intimation of the occurrence of a Lamprey in the 

 Australasian Colonies is to be found in the Ichthyology of the 

 Erebus and Terror, where Sir John Richai^dson describes this 

 species from a Tasmanian example, without, however, separating 

 it from the arctogeean genus Petroniyzon; six years later, however, 



* In large exaraples even this disappears. 



