518 NAINBRBIS QUADRICUSPIDA. 



Synonyms. 



1780. Nais quadricuspida, Fabricius. Fauna Groenl., p. 315, n. 296. 



1828. Nainereis „ De Blainville. Diet. Sc. Nat., lvii, p. 491. 



1843. Scoloplos „ CErsted. Gronl. Annul. Dorsibr., p. 200, f. 106—110. 



1849. Aricia „ Leuckart. Arch. f. Naturges., xv, p. 198, Tab. iii, f. 11. 



1851. ., quadricuspis, Grube. Fam. Ann el., pp. 68 and 135.1 



18-53. „ ,, Stimpson. Synops. Mar. Invert. Gr. Manan, p. 33. 



1863. Scoloplos quadricuspis, idem. Ann. Groenl. in Proc. Acad. Nat. Sc. Philad., p. 140. 



1865. ,, quadricuspida, De Quatrefages. Anne]., ii, p. 287. 



1867. Naidonereis ,, Malmgren. Annul. Polych., p. 73. 



1869. „ „ Mcintosh. Rep. Brit. Assoc, (1868), p. 338. 



1875. „ „ Ehlers. Zeitschr. f. wiss. Zool., Bd. xxv, p. 59, Taf. iv, f. 28. 



1878. „ „ Mcintosh. Trans. Linn. Soc, 2 ser., Zool. i, p. 504. 



1897. Aricia „ Birula. Zool. Mus. Kaiser. Akad. Wiss. St. Petersb., p. 20. 



1901. „ „ Whiteaves. Geol. Surv. Canada, No. 722, p. 79. 



1905. Naidonereis ,, Mcintosh. Ann. Nat. Hist., ser. 7, vol. xv, p. 48. 



Habitat. — Procured in numbers between tide-marks, Lochmaddy, August, 1865,, 

 generally under stones amidst sandy mud ; a young example under Lithot 1 1 amnion 

 between tide-marks, Lerwick, Shetland. 



Greenland (O. Fabricius). 



Head (Plate LXV, figs. 5 and 5 a) forming a rounded and somewhat button-shaped 

 process set on the peristomial segment, which forms a short cone and is two-ringed 

 (being notched on each side). 



Body about 3 ins. in length, tapering very slightly in front, but considerably 

 diminishing towards the tail, which ends somewhat abruptly in two rounded dorsal 

 papillae, and two short ventral cirri. 



The anterior region consists of thirteen segments with the specially modified ventral 

 division of the feet. The branchiae in the sole example commenced on the sixth foot, 

 but it may be that those on the dorsum of the body at the fifth foot had been lost. 

 They remain of comparatively large size to within eight or ten segments from the tip of 

 the tail. When fully formed, as at the tenth foot (Plate LXXXVII, fig. 5), the branchia 

 is a flattened and somewhat acutely lanceolate process. A convex border of some extent 

 intervenes between it and the slight elevation of the dorsal division of the foot bearing 

 a fan-like tuft of tapering bristles (Plate LXXXVI, fig. 2), which have smooth shafts 

 but spinose tips (with a marked bend) simulating cameration. The dorsal cirrus behind 

 has a somewhat enlarged base and gently tapered tip (which is not acute). A smooth 

 margin intervenes between this division and the slightly convex and long inferior 

 division, which has a prominent blunt lobe or papilla rather below its middle posteriorly, 

 directed downward and backward. A dense series of the strong and slightly brownish 

 curved (club-shaped) bristles (Plate LXXXVI, fig. 2 a) occupies the whole length of the 

 division, with here and there a long serrato-camerated tapering bristle or two projecting 

 beyond them. Most of these short and strong bristles show distinct serrations towards 

 the curve, as if they were developed from broken forriis. The tips of many are rounded, 



