BY J. DOUGLAS-OGILRY. 581 



Beginning then with specimen / which measures but four 

 inches and is the smallest of our series I find that it possesses 

 eight ventral plates, and the height of the body is not quite one- 

 half of the length, without caudal (as 1 to 2-10) ; this then is a 

 typical T. australis of Shaw, Cuvier, and Giinther. Passing on 

 now to specimen c, which measures over six inches we find that it 

 also possesses eight ventral plates, but that the height of the body 

 is rather more than half the length without caudal (as 1 to 1'90), 

 being therefore intermediate between the two forms. Specimen d 

 bears nine ventral plates, and its height is exactly halt the length 

 without caudal, thus not fulfilling the special requirements of either 

 form, but going far to show how little dependence can be placed on 

 such a variable character as the number of ventral plates ; this 

 example was taken at the same time and place as the preceding, 

 and is a trifle the larger. Specimen h is but little larger than /'/ 

 it bears but eight plates, but the last is twice as large as any of the 

 others, and appears like two normal plates soldered together ; I 

 have therefore placed it among those bearing nine plates ; the 

 height of the body is more (1 to 1-88) than half the length with- 

 out caudal ; this is therefore a typical T. jacksoniensis ; it measures 

 barely 5^ inches. Finally our last specimen, a, from the same 

 locality as c and c/, exceeds Mr. Macleay's limits, having no less 

 than twelve ventral plates, while the height of the body is exactly 

 one-half its length without caudal. 



To facilitate reference to their individual differences! heregivealist 

 of the examples showing the length, number of ventral plates, and 

 comparative height of each : — 



Total length in inches ... 

 Number of ventral plates 

 Height to length (s. c.) 



a. \ h. c. \ d. e. f. 



5-90 I 4-10 6-10 6-20 5-45 4.00 



12 I ?9 8 1 9 Jl 8 



1:2-00 i 1:1-88 1:1-90 1:200 1:1-85 1:210 



I have gone thus carefully into the details of each individual, in 

 order that, while stating it to be. my conviction, that from the 

 above facts the forms cannot be specifically separated, I can at the 

 same time leave each one at liberty to settle the question for 

 himself. 



