254 



R. COLLETT ON BAL^NOPTKRA BOKEALIS. [Feb. 2, 



individuals 320, in others as many as 3-40. No. 2 for instance had 

 on its right side only 318, on its left 328. The number appears to 

 be rarely the same in the two jaws of the same individual. 



The front plates were smfill, almost rudimentary, and formed 

 double rows ; these were difficidt to count. The greatest length was 

 attained at the commencement of the latter third of the series, where 

 as a rule they measured 550 to 600 millim.^ 



From these measurements it appears that the length and number 

 of the plates are not constantly greater in the right than in the left 

 jaw, also that there is no constant difference between the plates in 

 the two sexes. 



The hair-like bristles in which each plate terminates, and Avhich 

 form the most effective part of the straining-apparatus, are in this 

 species unusually fine, somewhat resembling silky wool, and white 



' I give liere the measurements of the baleen-plates of 4 examples, viz. those 

 of specimens Nos. 1, 3, and 5, and those of a fourth individual, the jaw of which 

 lay on the beach. They are reckoned from behind forwards, so that No. 50 lies 

 near the angle of the mouth. No. 250 nearest the symphysis of the jaw. They arc 

 measured from their base (in the freshly killed specimen) to the outei'most 

 point where the plates terminate and the bristles commence. 



No. 1. Female. Left all black : on the right side, the first 

 slightly lighter colour. 



Right side 324 plates. 



Left side 328 plates. 



millim. 



Length of no. 50 4(iO 



no. 100 590 



no. 150 620 



no. 200 420 



no. 250 240 



millim. 



No. 50 4;30 



„ 100 5fiO 



„ 150 510 



„ 200 420 



„ 250 240 



No. 3. Female. All black. 



Left side 334 plates. 



miUiui. 



Length of no. 50 4.30 



no. 100 520 



no. 150 490 



no. 200 380 



no. 250 180 



Right side 328 plates. 



No. 



.^0 

 100 

 150 

 200 

 250 



millim. 

 .. 450 

 .. 540 

 .. 470 

 .. 370 

 .. 210 



No. 5. Male. All black. 



Left side 318 plates. 



millim. 



Length of no. .50 490 



no. 100 ()40 



no. 1.50 .590 



no. 200 420 



no. 250 250 



Right side 321 plates. 



No. 



50 

 100 

 1.50 

 200 

 250 



millim. 

 .. 480 

 .. 630 

 .. 590 

 .. 440 

 .. 250 



Another example (sex miknown). All black. 



Left side 333 plates. 



No. 



50 



lot) 



150 

 200 

 250 



millim. 

 .. 450 

 .. 570 

 .. 520 

 .. 400 

 .. 250 



Right side 339 plates. 



No. 50 

 „ 100 

 „ 150 

 „ 200 

 „ 250 



millim. 

 .. 500 

 .. OOO 

 .. 5()0 

 .. 4."iO 

 .. 240 



