NEREIS (PERINEREIS) MABIONIL 295 



to the pelagic condition. From the description of Dr. Baird, moreover, the form he de- 

 scribed as Heteronereis signata is in all probability the epitokous condition of N. Schmard&i, 

 and accordingly it has been entered doubtfully under that species. The specimen could 

 not be found in the British Museum at the period of examination. 



The Nereis Sarsii of Rathke 1 has certain resemblances to this form, but it is difficult 

 to determine the exact relationships of the northern form. 



The grounds on which Malmgren (1867) founded the genus Praxithea, though 

 interesting in themselves, do not seem to be sufficient to warrant the separation. 



De St. Joseph procured his examples in coriaceous tubes amongst the mud of the 

 Zostera-flats in company with Gerianthus membranaceus, Haime. Gravier, 2 again, met 

 with this form in muddy tubes in the Zostera-region at St. Vaast-la-Hougue in August 

 and September, until it became transformed into a Heteronereis. 



The species is chiefly a southern one. 



4. Nereis (Perinekeis) Marionk, Audouin and Edwards, 1833. Plate LX, fig. 9— head ; 

 Plate LXXII, figs. 3-3 d— feet; Plate LXXXI, figs. 3 and 3 a— bristles. 



Specific Characters. — Head greenish mottled with dark pigment, but the posterior 

 border is pale. Eyes normal, brownish, with lenses anteriorly and occasionally 

 posteriorly. Dorsal of the first pair of tentacular cirri longest, cirrophore greenish, 

 ventral short and thick. All cirri somewhat short. Body 3 — 4 inches long ; peristomial 

 segment twice as broad as the next. Dull olive green anteriorly, paler posteriorly ; 

 whitish patch in front of each foot, and a little white pigment in the dorsal median line. 

 Lobes of the feet pale. Posteriorly are two short caudal cirri. Proboscis with strong 

 curved jaws having five teeth. Paragnathi feebly developed. Dorsally the basal region 

 in extrusion has two conspicuous papillae, each surmounted by a large brown tooth (VI), 

 and on the fold between them are two or three smaller teeth (V). The folds are 

 thirteen in number, and ventrally have minute paragnathi arranged on two sides of 

 each triangular area (VII and VIII), the apex being in front. In some each area is 

 tinted brownish. Dorsally in the maxillary region is a group of small teeth (II) on each 

 side, ventrally in the same region are rows of small paragnathi generally forming a 

 somewhat elongated area (IV) on each side, whilst between them is a considerable group 

 of small paragnathi (III). 



The first foot is characterized by the greater proportional bulk of the cirri; seti- 

 gerous lobe massive. About the thirtieth foot a considerable dorsal elevation appears, 

 and continues to the posterior end. It is marked by opaque granular glands. The 

 characteristic foot occurs near the fifty-seventh, in which the dorsal region — comprising 

 the dorsal lobe and the dorsal cirrus — is greatly hypertrophied, extending by-ancl-by, e g., 

 at the sixty-eighth, as a long lamella with the cirrus at the tip. The bristles are of two 

 kinds, the tapering tips of the homogomph being somewhat short, as are also those of the 

 heterogomph. 



1 ' Beitr. Fauna Xorweg./ p. 161, Taf. viii, f. 6—8, 1843. 



2 f Xouv. Arch. Mas./ p. 148, 1901. 



