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The difference in the form of the lingual teeth indicated by 

 the authors do not exist in Oeotria, and in Mordacia they are 

 similar, being, when seen in front, like two small horns, and, 

 when sideways, having the appearance of serrated arches. 



Not a. — I consider as belonging to the Ammoccetes type, or 

 larval stage, a singular little Petromyzonid, which was found in 

 the Tarra. The body is eel-shaped, naked, cylindrical, and 

 elongate, being tweuty-three times as long as high ; it is entirely 

 divided in annular rings, which appearance seems due to the 

 muscular flakes being very visible through the smooth skin. I 

 can see no teeth ; the upper lip is flat, and considerably prolon- 

 gated over the buccal aperture ; it is truncated in front, and this 

 part, seen upperly, is rather bifurcated. The lateral line is well 

 marked in all the length of the body ; there is only one dorsal, 

 which begins at about two-thirds of the length of the body, and 

 is joined with the caudal and the anal ; the latter is considerably 

 shorter than the dorsal ; these fins are all equal in their length ; 

 no eye visible. The skin of the throat is rather extensible ; the 

 prolongation of the upper lip over the lower is equal to the 

 height of the body ; the tail is pointed. 



The colour is of a light green, with the belly white ; on the 

 back extends a narrow longitudinal line ; the head and throat 

 are pink, and the fins of the same colour. Total length, four 

 and three-eighth inches. 



I should have thought this might be the first state of Geotria, 

 but we have just seen that I had a still smaller specimen of this, 

 which has entirely the form of the adult. In this state of things, 

 I propose giving provisionally to this the name of Yarra 

 Singularis. 



In a dried state, the prolongated part of the head is apt to 

 bend upwards, which gives the fish rather the appearance of a 

 Syngnathus. The branchial apparatus are visible ; the body is 

 remarkably soft, which makes it very difficult -to examine it ; no 

 barbels round the mouth. 



It was found in Captain Sinnot's dock, on the lower Tarra, in 

 brackish water. 



