782 J. H. ASHWOETH. 



Prost. Mid. Middle lobe of prostomium. Sp. Fragment of spicule. St. 

 Sloiiiacli. V. V. Ventral vessel. 



PLATE 30. 



Fig. 1. — Distal half of a seta from the fifth notopodium of a specimen of 

 Arenicola assimilis from Uscliuaia. X 100. 



Fig. 1a. — A portion of the seta more highly magnified. Note the lamina 

 on the left bearing fine teeth, x 750. 



Fig. 2. — Distal portion (two fifths) of a seta from the sixth notopodium of 

 a specimen of A. assimilis, var. affinis, from Otago Harbour, x 100. 



Fig. 2 a. — A portion of the same seta more highly magnified. Note the 

 broad lamina crossed by fine oblique lines, x 500. 



Figs. 3, 4, 5. — Notopodial seta3 from a post-larval specimen (7"0 mm. long) 

 of A. assimilis, var. affinis. Most of the setaj are of the kind shown in 

 Fig. 3, but in each notopodium there is one seta of the type seen in Fig. 5. 

 Setae of the kind shown in Fig. 4 are much less common than the preceding ; 

 only two specimens were seen in ten notopodia. The lamina is breaking up 

 on one side near its tip into fine teeth. X 320. 



Fig. 6. — Tip of a seta of the same kind as shown in Fig. 5. Note the fine 

 teetii on the margin of the lamina on one side, x GOO. 



Fig. 7. — A crotchet from the fifteenth neuropodium of an Otago specimen 

 (var. affinis). X 100. 



Fig. 8. — The head of a crotchet from another Otago sp3cimen, to show the 

 teeth situated on the sides of the rostrum, x 280. 



Fig. 9. — A crotchet from the fifteenth neuropodium of A. assimilis from 

 Uscliuaia. X 100, 



Fig. 10. — Two crotchets from the sixteenth neuropodium of a post-larval 

 specimen (7'(\ mm. long) of A. assimilis, var. affinis. A shows the appear- 

 ance of the ehffita when the rostrum and post-rostral teeth are in focus ; in J> 

 the teeth on the sides of the rostrum are also sliowii. Tlie subrostral process 

 is now seen to be one of the series of teeth. The dotted line indicates the 

 level of the epidermis. X GOO. 



Fig. 11.— Diagram of a portion of the ncrvc-cord of A. assimilis, var. 

 affinis, from Otago Harbour, to show the distribution of the giant nerve- 

 cells. The transverse lines indicate the position of the ncuropndia, the 

 numbers of which they boar. The nerve-cord is magnified about 10 times 

 and the cells 40 times. 



Fig. 12. — Diagram of a portion of the nerve-cord of A. assimilis from 

 Uscliuaia, l,o sliow the distribution of the giant nerve-cells. The trans- 

 verse lines indicate the position of the neuropodia. The last giant-cell shown 



