POST LARVAL STAGES OF AUSTRALIAN FISHES. 
149 
the surface by the rip of the ebbing tide. Welsh and Breder (1922) have 
shown that the related American 8. maculatus has adherent demersal eggs. 
The Noosa River eggs measured 0-94 millimetres in diameter and from them 
hatched larval toadfish which have been identified as our common species 
8. hamiltoni. At first there is a globular yolk-mass underneath the highly 
pigmented skin of that region which soon becomes the visceral region. The 
yolk is soon absorbed, and upon attaining a size of 2-0 millimetres a close 
resemblance to adult facies becomes apparent. 
Two distinct types of toadfish larvae have been collected in tow nets 
and adults of two species, namely 8. hamiltoni and 8. pleurogramma, commonly 
frequent southern Queensland estuaries. These larvae possess complete opercula, 
which in the adults of this family are reduced to small, rounded apertures 
situated anteriorly to the pectoral fins. Adult 8. pleurogramma differs from 
S. hamiltoni in the possession of a prominent spine at the base of the opercular 
opening. One type of planktonic larva (text figs. 7C and 7D) possess a 
prominent angular opercular border. The relationship of these larval types 
to the respective adults is thus evident on the basis of this character alone. 
The specific identification of these respective larvae was supported further by 
following through pigmentary changes until a size was reached where adult 
diagnostic characters were available. There is also correlation between the 
seasons of occurrence of these respective larval types and the seasons of 
appearance of small, recognisable postlarvae of both species in the weedy 
shallows of Noosa River and Bribie Passage. Larvae, identified as those 
of S. hamiltoni, were found in Noosa River plankton collections during April, 
June, September and October whilst those of S. pleurogramma have only been 
collected in August and September. The former species appears to have a more 
extended spawning season than the latter. 
The larvae of 8. hamiltoni are approximately 1-6 millimetres in length 
upon emergence from the egg and are pigmented similarly to the advanced 
egg-embryo of that species illustrated in text fig. 7 A. There is a mass of 
blackish chroma tophores on the frontal region of the head, another mass 
investing the yolk-sack and a third series forming a lateral patch on either 
side of the caudal myotonies. The latter group is composed of chromatophores 
longitudinally arranged in four or five almost parallel rows. There appears 
to be some slight difference in the pigmentation of the planktonic larvae of 
this species in respect to the month spawned. Those collected in June 1940 
have pigment arranged as above, but when this type have grown to about 
2-6 millimetres (text fig. 7E) there is an extension backwards of the head 
pigment to the level of the origin of the dorsal natatory fold. The scattered, 
stellate cells of the caudal flanks have become rearranged into dark patches 
along the dorsal and ventral somite margins, linking across the caudal regions 
in a diffuse band. The September larvae differ in lacking the caudal pigment 
completely and there are two patches of dorsal cells, one on the head and the 
other on the body somites near the origin of the dorsal natatory fold. 
A single larger postlarva, 4-6 millimetres in length, was collected in 
the Noosa River plankton at the surface on the 13th October, 1944. Its pigmen- 
tation is composed solely of dispersed, large, stellate, black cells arranged as 
