362 RECORDS "1 nil. AUSTRALIAN MUSEUM. 



colour-marking varies greatly in degree of development, 

 according to the age of the specimens. Again, as I have found 

 in P. tetricus, the young may bear no resemblance whatever, 

 either in form or colour to the adults, and I have good reason 

 to suppose that similar changes occur in ]', gymnogenis and 

 1'. parilus. 



The colour variation has already been noted by Johnston 6 as 

 follows: — " I consider the classification of the genus Labrichthys 

 to be far from satisfactory. I have good reason to believe that 

 dependence upon colour-markings, however peculiar and brilliant, 

 is to a great extent delusive. Like the genus Monocanthus, 

 many of them change colour with age." 



One of the most striking changes in form with growth is the 

 alteration of the form of the head. In the young it is more or 



less conical, the snout being pointed, whereas in adults the upper 

 and lower profiles become convex, so that the head is larger and 

 broader; the eye, also, is proportionately much smaller in adults. 

 In some species in which the fins are not covered with scales 

 the small body scales near the bases of the dorsal and anal may 

 be so crowded in young specimens that they overlap the extreme 

 bases of those tins : as the body increases in size they have more 

 room and arc then confined to their proper place. In the young 

 the tubules of the lateral line are much less branched than in 

 older specimens. Finally, the forms of the pectoral and caudal 

 tins vary considerably, the latter being often rounded in the 

 yonng, and truncate or even emarginate in adults: the upper 

 rays of the pectoral sometimes grow out beyond the margin ol 

 the rest of the fin. 



With all this extraordinary variation it is difficuH to find 

 characters by which the various species may be distinguished, 

 but in the following key and diagnoses I have selected such as 

 seemed to be constant in the specimens available to me, 



.1.— 1). ix. / 12, A. iii. LO-11. Body elongate. Pectoral fin 



rounded. El I i.i 1. 1< li I HYS. 



.1.1. — I), ix. 1 1. A. iii. 1". Body not elongate. 



II. — Pectoral fin rounded. Membrane of dorsal and anal 

 fins not produced beyond the spines as free pencils. 



Pli III \l.|.l s 



/•'/■'. Pectoral fin not rounded, the upper rays at leas! as 

 long as i lie middle ones. 



• .I'.lmston — Proc. Boy. Sec. Tasm., ISM (1882), i>. 124. 



